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  • Should database-models (conceptual or physical) be reviewed by DBAs?

    - by user61852
    Where I work, new applications that are being developed that will use their own relational database, must have their database-models (conceptual, then physical ) reviewed and aproved by DBAs. Things looked after are normalization, antipatterns, table and column naming standards, etc. Is this really a DBA's responsability to do this ? or should it be, in a greater extend, the responsability of app designers and architects ?

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  • What would a database look like if it were normalized to be completely abstracted? lets call it Max(n) normal form

    - by Doug Chamberlain
    edit: By simplest form i was not implying that it would be easy to understand. For instance, developing in low level assembly language is the simplest way to can develop code, but it is far from the easiest. Essentially, what I am asking is in math you can simplify a fraction to a point where it can no longer be simplfied. Can the same be true for a database and what would a database look like in its simplest, form?

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  • PostgreSQL 9.1 Database Replication Between Two Production Environments with Load Balancer

    - by littleK
    I'm investigating different solutions for database replication between two PostgreSQL 9.1 databases. The setup will include two production servers on the cloud (Amazon EC2 X-Large Instances), with an elastic load balancer. What is the typical database implementation for for this type of setup? A master-master replication (with Bucardo or rubyrep)? Or perhaps use only one shared database between the two environments, with a shared disk failover? I've been getting some ideas from http://www.postgresql.org/docs/9.0/static/different-replication-solutions.html. Since I don't have a lot of experience in database replication, I figured I would ask the experts. What would you recommend for the described setup?

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  • How should I copy the "mysql" database to my new server using PHPMyAdmin

    - by undefined
    My new webhosting company has set up a MySQL database for me and it has the tables MySQL and Information_schema already there. I want to copy my existing database from another server (a) to the new one (b). I assume I need to overwrite the 'mysql' database on server (b) with the one from my existing server (a) or atleast copy over the permissions. 1) What information does the mysql database hold? users and permissions I can see, does it have the login info for phpMyAdmin? I dont want to overwrite that obviously. 2) Should I drop the table on server (b) and import my original? 3) Should I just copy the users table? 4) Do I need to worry about the information_schema table? should I copy this over too? thanks

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  • Oracle Database 12c ????????(?????)

    - by OTN-J Master
    Oracle Database 12c????????????? ?????????????????????????????????????¦ ??????????????? ????????? Oracle Database 12c????OTN??? Oracle Database 12c???? ¦ Oracle Database 12c???????????????? Oracle Database 12c ?????? (PDF)¦ Oracle Database 12c???????????? ??????????????? Oracle Database 12c (??????????????) "Oracle Database 12c???"??????????????????? ??????NEC???????????????? ???????????????????????¦ Oracle Database 12c??????????????????? ???????????Oracle Database 12c ????? (PC/????????????!) ????????????????????????????? ?????????????????! Oracle Database 12c???????? (@IT /Database Expert) ??????Oracle Database 12c????????·?????????????????? (EnterpriseZine/DB Online) ??????????!Oracle Database 12c???? (EnterpriseZine/DB Online) ¦ Oracle Database 12c?????????????????????? ??????????Oracle Database 12c ?????!  (EnterpriseZine/DB Online) ¦ Oracle Database 12c???????????? ????????? OTN???????????????????????????????????????????? ?????????/??????? ~????????????????12c??????????!~ Oracle Database 12c????????!???????????? ¦ Oracle Database 12c??????????????????? Oracle University?? Oracle Database 12c: ?????? ¦ Oracle Database 12c?????????????????????????? ?????????????????? ¦ Oracle Database 12c????????????????? ?????????????????????????????????????????(??)???????????????????????????OTN Community(??????)?????????OTN Community??? ¦ Oracle Database 12c???????????????? 12c????????????????????????OTN????????????????Twitter(@oracletechnetjp)???????????????????????! ????????????????????????????Oracle Database 12c???????????????(?8???????????&??????????)????????

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  • 2?????????????(Database??)

    - by rika.tokumichi
    ???????????OTN????????? ??????????????????????????????????????????????????????? ????????????????????????????????????????? ???Database??????????????2?????????????????????????????????? ??????????? 1?:Oracle SQL Developer 2.1 (2.1.0.63.73)?Download? 2?:Oracle Database 11g Release 1?Download? 3?:Oracle Database 10g Express Edition?Download? 4?:Oracle Database 10g Release 2?Download? 5?:Oracle Database 11g Release 2?Download? (????2?1?~2?28?) ??????1??2??????????! ?????TOP5?????????????????????????? ??12????????????????????????????? ???Oracle Database 11g Release2?????Grid Infrastructure???? ??Grid Infrastructure??????????Oracle Clusterware?Oracle Automatic Storage Management(ASM)???????? ??????·????????????????????????????????????????????? ????????????????????OTN???????????????????????????????? >?????:Oracle Database 11g R2?????Oracle VM???????????? ??10?30????????????Oracle VM Forum 2009????????????????2009?9?????????Oracle Database 11g Release 2??????????????????????????????????????????????????????????????????????????????????????????????????????? >???:???????????????????2(???????) ????????????????????????????????????????????????????????????????????????????2???????????(????????????????)????????????????????????????????????????????????????? >Oracle Database 11g Release 2???????? ?????????????????????????????????????????????????????????? ???????????

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  • Users in database server or database tables

    - by Batcat
    Hi all, I came across an interesting issue about client server application design. We have this browser based management application where it has many users using the system. So obvisously within that application we have an user management module within it. I have always thought having an user table in the database to keep all the login details was good enough. However, a senior developer said user management should be done in the database server layer if not then is poorly designed. What he meant was, if a user wants to use the application then a user should be created in the user table AND in the database server as a user account as well. So if I have 50 users using my applications, then I should have 50 database server user logins. I personally think having just one user account in the database server for this database was enough. Just grant this user with the allowed privileges to operate all the necessary operation need by the application. The users that are interacting with the application should have their user accounts created and managed within the database table as they are more related to the application layer. I don't see and agree there is need to create a database server user account for every user created for the application in the user table. A single database server user should be enough to handle all the query sent by the application. Really hope to hear some suggestions / opinions and whether I'm missing something? performance or security issues? Thank you very much.

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  • Oracle Database Smart Flash Cache: Only on Oracle Linux and Oracle Solaris

    - by sergio.leunissen
    Oracle Database Smart Flash Cache is a feature that was first introduced with Oracle Database 11g Release 2. Only available on Oracle Linux and Oracle Solaris, this feature increases the size of the database buffer cache without having to add RAM to the system. In effect, it acts as a second level cache on flash memory and will especially benefit read-intensive database applications. The Oracle Database Smart Flash Cache white paper concludes: Available at no additional cost, Database Smart Flash Cache on Oracle Solaris and Oracle Linux has the potential to offer considerable benefit to users of Oracle Database 11g Release 2 with disk-bound read-mostly or read-only workloads, through the simple addition of flash storage such as the Sun Storage F5100 Flash Array or the Sun Flash Accelerator F20 PCIe Card. Read the white paper.

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  • Class Loading Deadlocks

    - by tomas.nilsson
    Mattis follows up on his previous post with one more expose on Class Loading Deadlocks As I wrote in a previous post, the class loading mechanism in Java is very powerful. There are many advanced techniques you can use, and when used wrongly you can get into all sorts of trouble. But one of the sneakiest deadlocks you can run into when it comes to class loading doesn't require any home made class loaders or anything. All you need is classes depending on each other, and some bad luck. First of all, here are some basic facts about class loading: 1) If a thread needs to use a class that is not yet loaded, it will try to load that class 2) If another thread is already loading the class, the first thread will wait for the other thread to finish the loading 3) During the loading of a class, one thing that happens is that the <clinit method of a class is being run 4) The <clinit method initializes all static fields, and runs any static blocks in the class. Take the following class for example: class Foo { static Bar bar = new Bar(); static { System.out.println("Loading Foo"); } } The first time a thread needs to use the Foo class, the class will be initialized. The <clinit method will run, creating a new Bar object and printing "Loading Foo" But what happens if the Bar object has never been used before either? Well, then we will need to load that class as well, calling the Bar <clinit method as we go. Can you start to see the potential problem here? A hint is in fact #2 above. What if another thread is currently loading class Bar? The thread loading class Foo will have to wait for that thread to finish loading. But what happens if the <clinit method of class Bar tries to initialize a Foo object? That thread will have to wait for the first thread, and there we have the deadlock. Thread one is waiting for thread two to initialize class Bar, thread two is waiting for thread one to initialize class Foo. All that is needed for a class loading deadlock is static cross dependencies between two classes (and a multi threaded environment): class Foo { static Bar b = new Bar(); } class Bar { static Foo f = new Foo(); } If two threads cause these classes to be loaded at exactly the same time, we will have a deadlock. So, how do you avoid this? Well, one way is of course to not have these circular (static) dependencies. On the other hand, it can be very hard to detect these, and sometimes your design may depend on it. What you can do in that case is to make sure that the classes are first loaded single threadedly, for example during an initialization phase of your application. The following program shows this kind of deadlock. To help bad luck on the way, I added a one second sleep in the static block of the classes to trigger the unlucky timing. Notice that if you uncomment the "//Foo f = new Foo();" line in the main method, the class will be loaded single threadedly, and the program will terminate as it should. public class ClassLoadingDeadlock { // Start two threads. The first will instansiate a Foo object, // the second one will instansiate a Bar object. public static void main(String[] arg) { // Uncomment next line to stop the deadlock // Foo f = new Foo(); new Thread(new FooUser()).start(); new Thread(new BarUser()).start(); } } class FooUser implements Runnable { public void run() { System.out.println("FooUser causing class Foo to be loaded"); Foo f = new Foo(); System.out.println("FooUser done"); } } class BarUser implements Runnable { public void run() { System.out.println("BarUser causing class Bar to be loaded"); Bar b = new Bar(); System.out.println("BarUser done"); } } class Foo { static { // We are deadlock prone even without this sleep... // The sleep just makes us more deterministic try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Bar b = new Bar(); } class Bar { static { try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Foo f = new Foo(); }

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  • Database Consolidation onto Private Clouds - updated for Oracle Database 12c

    - by B R Clouse
    One of our team's most popular white papers has been expanded and updated to discuss Oracle Database 12c.  Now available on our OTN page, the new version of Database Consolidation onto Private Clouds covers best practices for consolidation with pluggable databases that the new mulitenant architecture provides, and expanded information on the database and schema consolidation options.  These are the consolidation models the paper evaluates:   server  database  schema pluggable databases  Key considerations for consolidating workloads which the paper explores: Choosing a consolidation model How PDBs solve the IT complexity problem Isolation in consolidated environments Cloud pool design Complementary workloads Enterprise Manager 12c for consolidation planning and operations Many more white papers have been updated or are new for Oracle Database 12c. We'll continue to highlight those which tie directory to your journey to enterprise cloud.

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  • What do you look for when debugging deadlocks?

    - by Michael K
    Recently I've been working on projects that heavily use threading. I think that I'm OK at designing them; use stateless design as much as possible, lock access to all resources that more than one thread needs, etc. My experience in functional programming has helped that immensely. However, when reading other people's thread code, I get confused. I am debugging a deadlock right now, and since the coding style and design are different from my personal style, I am having a difficult time seeing potential deadlock conditions. What do you look for when debugging deadlocks?

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  • Database Server Hardware components (order of importance), CPU speed VS CPU cache vs RAM vs DISK

    - by nulltorpedo
    I am new to database world and would like to know what are crucial hardware specs when it comes to database performance. I have searched the internet and found this so far (In order of decreasing importance): 1) Hard Disk: Get an SSD basically (much more IOPS than spinners) 2) Memory: Get as much as you can afford 3) CPU: For the same $ spent, prefer larger cache size over speed. Are these findings sensible? EDIT: I would like to focus on CPU speed VS CPU cache size. EDIT2: The database is used to store some combination of ints and int arrays with few text fields. There are a lot of Select queries looking for existing entries. If entry is not found, then insert it. I would say most of processing would be trying to find a match across a table with 200 columns and 20k rows. The insert statements are very few. EDIT3: Also, we have a lot of views (basically select queries).

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  • SYS2 Scripts Updated – Scripts to monitor database backup, database space usage and memory grants now available

    - by Davide Mauri
    I’ve just released three new scripts of my “sys2” script collection that can be found on CodePlex: Project Page: http://sys2dmvs.codeplex.com/ Source Code Download: http://sys2dmvs.codeplex.com/SourceControl/changeset/view/57732 The three new scripts are the following sys2.database_backup_info.sql sys2.query_memory_grants.sql sys2.stp_get_databases_space_used_info.sql Here’s some more details: database_backup_info This script has been made to quickly check if and when backup was done. It will report the last full, differential and log backup date and time for each database. Along with these information you’ll also get some additional metadata that shows if a database is a read-only database and its recovery model: By default it will check only the last seven days, but you can change this value just specifying how many days back you want to check. To analyze the last seven days, and list only the database with FULL recovery model without a log backup select * from sys2.databases_backup_info(default) where recovery_model = 3 and log_backup = 0 To analyze the last fifteen days, and list only the database with FULL recovery model with a differential backup select * from sys2.databases_backup_info(15) where recovery_model = 3 and diff_backup = 1 I just love this script, I use it every time I need to check that backups are not too old and that t-log backup are correctly scheduled. query_memory_grants This is just a wrapper around sys.dm_exec_query_memory_grants that enriches the default result set with the text of the query for which memory has been granted or is waiting for a memory grant and, optionally, its execution plan stp_get_databases_space_used_info This is a stored procedure that list all the available databases and for each one the overall size, the used space within that size, the maximum size it may reach and the auto grow options. This is another script I use every day in order to be able to monitor, track and forecast database space usage. As usual feedbacks and suggestions are more than welcome!

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  • Learn to use PHP and Python with Oracle Database

    - by christopher.jones
    The Oracle Learning Library has posted up the latest "Oracle By Example" labs giving an introduction to PHP & Python with the Oracle Database : Using PHP with Oracle Database 11g - a basic introduction Developing a PHP Web Application with Oracle Database 11g - a Zend Framework application using the NetBeans IDE Using Python With Oracle Database 11g - a basic introduction Using the Django Framework with Python and Oracle Database 11g - a basic web application

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  • Oracle Database Insider Now on LinkedIn

    - by Troy Kitch
    Our close friends over at the Oracle Database Insider blog have recently started a LinkedIn discussion group. Go behind the scenes of the latest Oracle Database announcements and discussions that include Oracle Database 11g and its options, such as Database Security, and the newest product, Oracle Exadata. Come on over to post a discussion topic, an event, ask questions and stay up-to-date on the latest Oracle Database information. We'll be there to join the discussions and answer questions. Join us on LinkedIn's latest group!

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  • SQL SERVER – Spatial Database Queries – What About BLOB – T-SQL Tuesday #006

    - by pinaldave
    Michael Coles is one of the most interesting book authors I have ever met. He has a flair of writing complex stuff in a simple language. There are a very few people like that.  I really enjoyed reading his recent book, Expert SQL Server 2008 Encryption. I strongly suggest taking a look at it. This blog is written in response to T-SQL Tuesday #006: “What About BLOB? by Michael Coles. Spatial Database is my favorite subject. Since I did my TechEd India 2010 presentation, I have enjoyed this subject a lot. Before I continue this blog post, there are a few other blog posts, so I suggest you read them.  To help build the environment run the queries, I am going to present them in this single blog post. SQL SERVER – What is Spatial Database? – Developing with SQL Server Spatial and Deep Dive into Spatial Indexing This blog post explains the basics of Spatial Database and also provides a good introduction to Indexing concept. SQL SERVER – World Shapefile Download and Upload to Database – Spatial Database This blog post will enable you with how to load the shape file into database. SQL SERVER – Spatial Database Definition and Research Documents This blog post links to the white paper about Spatial Database written by Microsoft experts. SQL SERVER – Introduction to Spatial Coordinate Systems: Flat Maps for a Round Planet This blog post links to the white paper explaining coordinate system, as written by Microsoft experts. After reading the above listed blog posts, I am very confident that you are ready to run the following script. Once you create a database using the World Shapefile, as mentioned in the second link above,you can display the image of India just like the following. Please note that this is not an accurate political map. The boundary of this map has many errors and it is just a representation. You can run the following query to generate the map of India from the database spatial which you have created after following the instructions here. USE Spatial GO -- India Map SELECT [CountryName] ,[BorderAsGeometry] ,[Border] FROM [Spatial].[dbo].[Countries] WHERE Countryname = 'India' GO Now, let us find the longitude and latitude of the two major IT cities of India, Hyderabad and Bangalore. I find their values as the following: the values of longitude-latitude for Bangalore is 77.5833300000 13.0000000000; for Hyderabad, longitude-latitude is 78.4675900000 17.4531200000. Now, let us try to put these values on the India Map and see their location. -- Bangalore DECLARE @GeoLocation GEOGRAPHY SET @GeoLocation = GEOGRAPHY::STPointFromText('POINT(77.5833300000 13.0000000000)',4326).STBuffer(20000); -- Hyderabad DECLARE @GeoLocation1 GEOGRAPHY SET @GeoLocation1 = GEOGRAPHY::STPointFromText('POINT(78.4675900000 17.4531200000)',4326).STBuffer(20000); -- Bangalore and Hyderabad on Map of India SELECT name, [GeoLocation] FROM [IndiaGeoNames] I WHERE I.[GeoLocation].STDistance(@GeoLocation) <= 0 UNION ALL SELECT name, [GeoLocation] FROM [IndiaGeoNames] I WHERE I.[GeoLocation].STDistance(@GeoLocation1) <= 0 UNION ALL SELECT '',[Border] FROM [Spatial].[dbo].[Countries] WHERE Countryname = 'India' GO Now let us quickly draw a straight line between them. DECLARE @GeoLocation GEOGRAPHY SET @GeoLocation = GEOGRAPHY::STPointFromText('POINT(78.4675900000 17.4531200000)',4326).STBuffer(10000); DECLARE @GeoLocation1 GEOGRAPHY SET @GeoLocation1 = GEOGRAPHY::STPointFromText('POINT(77.5833300000 13.0000000000)',4326).STBuffer(10000); DECLARE @GeoLocation2 GEOGRAPHY SET @GeoLocation2 = GEOGRAPHY::STGeomFromText('LINESTRING(78.4675900000 17.4531200000, 77.5833300000 13.0000000000)',4326) SELECT name, [GeoLocation] FROM [IndiaGeoNames] I WHERE I.[GeoLocation].STDistance(@GeoLocation) <= 0 UNION ALL SELECT name, [GeoLocation] FROM [IndiaGeoNames] I1 WHERE I1.[GeoLocation].STDistance(@GeoLocation1) <= 0 UNION ALL SELECT '' name, @GeoLocation2 UNION ALL SELECT '',[Border] FROM [Spatial].[dbo].[Countries] WHERE Countryname = 'India' GO Let us use the distance function of the spatial database and find the straight line distance between this two cities. -- Distance Between Hyderabad and Bangalore DECLARE @GeoLocation GEOGRAPHY SET @GeoLocation = GEOGRAPHY::STPointFromText('POINT(78.4675900000 17.4531200000)',4326) DECLARE @GeoLocation1 GEOGRAPHY SET @GeoLocation1 = GEOGRAPHY::STPointFromText('POINT(77.5833300000 13.0000000000)',4326) SELECT @GeoLocation.STDistance(@GeoLocation1)/1000 'KM'; GO The result of above query is as displayed in following image. As per SQL Server, the distance between these two cities is 501 KM, but according to what I know, the distance between those two cities is around 562 KM by road. However, please note that roads are not straight and they have lots of turns, whereas this is a straight-line distance. What would be more accurate is the distance between these two cities by air travel. When we look at the air travel distance between Bangalore and Hyderabad, the total distance covered is 495 KM, which is very close to what SQL Server has estimated, which is 501 KM. Bravo! SQL Server has accurately provided the distance between two of the cities. SQL Server Spatial Database can be very useful simply because it is very easy to use, as demonstrated above. I appreciate your comments, so let me know what your thoughts and opinions about this are. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Spatial Database

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  • Webcast - Oracle Database In-Memory Option

    - by Thanos Terentes Printzios
    Next to the recent announcement by Larry Ellison on the Future of the Database, we are happy to share this exclusive series of live webcasts from Oracle Database Product Management, where you can learn more about the brand new Oracle Database 12c In-Memory option. Oracle Database In-Memory is Oracle’s new memory-optimized technology that transparently accelerates analytic, data warehousing, and reporting workloads, while also accelerating transaction processing (OLTP) workloads. Participants will learn about Oracle Database In-Memory benefits, features, and leading edge architecture.  The Database In-Memory architecture provides the ability to easily process data orders of magnitude faster by simply enabling the feature and identifying tables to bring in-memory without application changes. Details on Oracle Database In-Memory’s ease of use and management, scalability, and availability will also be covered. Please join us to learn more about Oracle Database In-Memory and get first-hand knowledge of this important new feature. Delivery Format This FREE online LIVE eSeminar will be delivered over the Web.These Oracle webcasts are FREE for Customers, System Integrators, ISVs, VARs and Platform Partners. Presenter: Richard Jacobs, Oracle Solution Architect  Europe Webcast 1 Date: August 29, 2014 @ 10:00 am to 11:00 am Central European Summer Time (CEST)Register Here! Europe Webcast 2 Date: September 29, 2014 @ 10:00 am to 11:00 am Central European Summer Time (CEST)Register Here!

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  • Should I comment Tables or Columns in my database?

    - by jako
    I like to comment my code with various information, and I think most people nowadays do so while writing some code. But when it comes to database tables or columns, I have never seen anyone setting some comments, and, to be honest, I don't even think of looking for comments there. So I am wondering if some people are commenting their DB strcuture here, and if I should bother commenting, for instance when I create a new column to an existing table?

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  • ASP.NET Website Administration Tool: Unable to connect to SQL Server database

    - by MedicineMan
    I am trying to get authentication and authorization working with my ASP MVC project. I've run the aspnet_regsql.exe tool without any problem and see the aspnetdb database on my server (using the Management Studio tool). my connection string in my web.config is: <connectionStrings> <add name="ApplicationServices" connectionString="data source=MYSERVERNAME;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true" providerName="System.Data.SqlClient" /> The error I get is: There is a problem with your selected data store. This can be caused by an invalid server name or credentials, or by insufficient permission. It can also be caused by the role manager feature not being enabled. Click the button below to be redirected to a page where you can choose a new data store. The following message may help in diagnosing the problem: Unable to connect to SQL Server database. In the past, I have had trouble connecting to my database because I've needed to add users. Do I have to do something similar here?

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  • Firebird database corruption causes

    - by Rytis
    I am running several different Firebird versions (2.0, 2.1) on multiple entry level Windows-based servers with wildly varying hardware. The only matching thing between them is that they are running same home built application with the same database structure. Lately I've been seeing massive slowdowns on multiple servers. Turns out that database gets corrupted, so each time it breaks, I get to mend, backup and restore the database, and it all is fine for some time (1-2 weeks), and then it repeats once again. Thankfully, I haven't seen any data loss or damage... yet. The thing is that every such downtime results in lost productivity, and often quite some driving for me as some of the databases are in remote locations. I've been trying to find out what's causing the corruption, but I haven't been able to. The fact that it's running on different hardware hints that it should not be a hardware based problem. If we rule out hardware issues, I have a bad feeling that it's a bug in Firebird as I'm not doing anything fancy via SQL. Do you have any idea how to find out exactly what's causing the corruption and hopefully fix the problem?

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  • What is the best way to do testing database (MYSQL spesific)

    - by justjoe
    Right now i'm on testing something in a database. It's a wordpress database. i have to write and delete and do other operation on it. As you know it, it has indexing mechanism that will always make every new post inherit the next highest possible ID. Please consider that this database is a copying of used database. it has been written before. So, i will need to make sure when i finish my testing, it will be the same Right now, my only solution is making backup. So if i have end in some section of planned testing, i will backup it and start next testing on another copy of it. Fortunately, the size of database is only a small one. so delete and copy and backup it will be easy. but i know this way of database testing is only partial solution.It force me to create too many backup copy. I don't know what i will do if the database has bigger size. it will be a very long of testing nightmare. so i wonder is there any solution that work just like rollback. So it will just lock the database and just put new entry as some kind of cache. I can erase it or write it into the database. i use mysql and phpmyadmin and use it to developed some custom solution. EDIT ::: How to effectively doing testing on database when developing PHP solution ?

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  • Need help choosing database server

    - by The Pretender
    Good day everyone. Recently I was given a task to develop an application to automate some aspects of stocks trading. While working on initial architecture, the database dilemma emerged. What I need is a fast database engine which can process huge amounts of data coming in very fast. I'm fairly experienced in general programming, but I never faced a task of developing a high-load database architecture. I developed a simple MSSQL database schema with several many-to-many relationships during one of my projects, but that's it. What I'm looking for is some advice on choosing the most suitable database engine and some pointers to various manuals or books which describe high-load database development. Specifics of the project are as follows: OS: Windows NT family (Server 2008 / 7) Primary platform: .NET with C# Database structure: one table to hold primary items and two or three tables with foreign keys to the first table to hold additional information. Database SELECT requirements: Need super-fast selection by foreign keys and by combination of foreign key and one of the columns (presumably DATETIME) Database INSERT requirements: The faster the better :) If there'll be significant performance gain, some parts can be written in C++ with managed interfaces to the rest of the system. So once again: given all that stuff I just typed, please give me some advice on what the best database for my project is. Links or references to some manuals and books on the subject are also greatly appreciated. EDIT: I'll need to insert 3-5 rows in 2 tables approximately once in 30-50 milliseconds and I'll need to do SELECT with 0-2 WHERE clauses queries with similar rate.

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  • SQL SERVER – How to Recover SQL Database Data Deleted by Accident

    - by Pinal Dave
    In Repair a SQL Server database using a transaction log explorer, I showed how to use ApexSQL Log, a SQL Server transaction log viewer, to recover a SQL Server database after a disaster. In this blog, I’ll show you how to use another SQL Server disaster recovery tool from ApexSQL in a situation when data is accidentally deleted. You can download ApexSQL Recover here, install, and play along. With a good SQL Server disaster recovery strategy, data recovery is not a problem. You have a reliable full database backup with valid data, a full database backup and subsequent differential database backups, or a full database backup and a chain of transaction log backups. But not all situations are ideal. Here we’ll address some sub-optimal scenarios, where you can still successfully recover data. If you have only a full database backup This is the least optimal SQL Server disaster recovery strategy, as it doesn’t ensure minimal data loss. For example, data was deleted on Wednesday. Your last full database backup was created on Sunday, three days before the records were deleted. By using the full database backup created on Sunday, you will be able to recover SQL database records that existed in the table on Sunday. If there were any records inserted into the table on Monday or Tuesday, they will be lost forever. The same goes for records modified in this period. This method will not bring back modified records, only the old records that existed on Sunday. If you restore this full database backup, all your changes (intentional and accidental) will be lost and the database will be reverted to the state it had on Sunday. What you have to do is compare the records that were in the table on Sunday to the records on Wednesday, create a synchronization script, and execute it against the Wednesday database. If you have a full database backup followed by differential database backups Let’s say the situation is the same as in the example above, only you create a differential database backup every night. Use the full database backup created on Sunday, and the last differential database backup (created on Tuesday). In this scenario, you will lose only the data inserted and updated after the differential backup created on Tuesday. If you have a full database backup and a chain of transaction log backups This is the SQL Server disaster recovery strategy that provides minimal data loss. With a full chain of transaction logs, you can recover the SQL database to an exact point in time. To provide optimal results, you have to know exactly when the records were deleted, because restoring to a later point will not bring back the records. This method requires restoring the full database backup first. If you have any differential log backup created after the last full database backup, restore the most recent one. Then, restore transaction log backups, one by one, it the order they were created starting with the first created after the restored differential database backup. Now, the table will be in the state before the records were deleted. You have to identify the deleted records, script them and run the script against the original database. Although this method is reliable, it is time-consuming and requires a lot of space on disk. How to easily recover deleted records? The following solution enables you to recover SQL database records even if you have no full or differential database backups and no transaction log backups. To understand how ApexSQL Recover works, I’ll explain what happens when table data is deleted. Table data is stored in data pages. When you delete table records, they are not immediately deleted from the data pages, but marked to be overwritten by new records. Such records are not shown as existing anymore, but ApexSQL Recover can read them and create undo script for them. How long will deleted records stay in the MDF file? It depends on many factors, as time passes it’s less likely that the records will not be overwritten. The more transactions occur after the deletion, the more chances the records will be overwritten and permanently lost. Therefore, it’s recommended to create a copy of the database MDF and LDF files immediately (if you cannot take your database offline until the issue is solved) and run ApexSQL Recover on them. Note that a full database backup will not help here, as the records marked for overwriting are not included in the backup. First, I’ll delete some records from the Person.EmailAddress table in the AdventureWorks database.   I can delete these records in SQL Server Management Studio, or execute a script such as DELETE FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 Then, I’ll start ApexSQL Recover and select From DELETE operation in the Recovery tab.   In the Select the database to recover step, first select the SQL Server instance. If it’s not shown in the drop-down list, click the Server icon right to the Server drop-down list and browse for the SQL Server instance, or type the instance name manually. Specify the authentication type and select the database in the Database drop-down list.   In the next step, you’re prompted to add additional data sources. As this can be a tricky step, especially for new users, ApexSQL Recover offers help via the Help me decide option.   The Help me decide option guides you through a series of questions about the database transaction log and advises what files to add. If you know that you have no transaction log backups or detached transaction logs, or the online transaction log file has been truncated after the data was deleted, select No additional transaction logs are available. If you know that you have transaction log backups that contain the delete transactions you want to recover, click Add transaction logs. The online transaction log is listed and selected automatically.   Click Add if to add transaction log backups. It would be best if you have a full transaction log chain, as explained above. The next step for this option is to specify the time range.   Selecting a small time range for the time of deletion will create the recovery script just for the accidentally deleted records. A wide time range might script the records deleted on purpose, and you don’t want that. If needed, you can check the script generated and manually remove such records. After that, for all data sources options, the next step is to select the tables. Be careful here, if you deleted some data from other tables on purpose, and don’t want to recover them, don’t select all tables, as ApexSQL Recover will create the INSERT script for them too.   The next step offers two options: to create a recovery script that will insert the deleted records back into the Person.EmailAddress table, or to create a new database, create the Person.EmailAddress table in it, and insert the deleted records. I’ll select the first one.   The recovery process is completed and 11 records are found and scripted, as expected.   To see the script, click View script. ApexSQL Recover has its own script editor, where you can review, modify, and execute the recovery script. The insert into statements look like: INSERT INTO Person.EmailAddress( BusinessEntityID, EmailAddressID, EmailAddress, rowguid, ModifiedDate) VALUES( 70, 70, N'[email protected]' COLLATE SQL_Latin1_General_CP1_CI_AS, 'd62c5b4e-c91f-403f-b630-7b7e0fda70ce', '20030109 00:00:00.000' ); To execute the script, click Execute in the menu.   If you want to check whether the records are really back, execute SELECT * FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 As shown, ApexSQL Recover recovers SQL database data after accidental deletes even without the database backup that contains the deleted data and relevant transaction log backups. ApexSQL Recover reads the deleted data from the database data file, so this method can be used even for databases in the Simple recovery model. Besides recovering SQL database records from a DELETE statement, ApexSQL Recover can help when the records are lost due to a DROP TABLE, or TRUNCATE statement, as well as repair a corrupted MDF file that cannot be attached to as SQL Server instance. You can find more information about how to recover SQL database lost data and repair a SQL Server database on ApexSQL Solution center. There are solutions for various situations when data needs to be recovered. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Curing the Database-Application mismatch

    - by Phil Factor
    If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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  • What is the best database design and/or software to model a thesaurus?

    - by Miles O'Keefe
    I would like to design a web app that functions as a simple thesaurus : a long list of words with attributes, all of which are linked to each other. Wikipedia defines it as: In Information Science, Library Science, and Information Technology, specialized thesauri are designed for information retrieval. They are a type of controlled vocabulary, for indexing or tagging purposes. Such a thesaurus can be used as the basis of an index for online material. The Art and Architecture Thesaurus, for example, is used to index the Canadian Information retrieval thesauri are formally organized so that existing relationships between concepts are made explicit. What database software, design or model would best fit this? Are PHP and MySQL good technologies to handle it?

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