I am using sqlite in c++ windows, And I have a db size about 60M, When I open the sqlite db, It takes about 13 second.

sqlite3* mpDB;
nRet = sqlite3_open16(szFile, &mpDB); 

And if I closed my application and reopen it again. It takse only less then 1 second.

First, I thought It is because of disk cache. So I preload the 60M db file before sqlite open, and read the file using CFile, However, after preloading, the first time is still very slow.

    BOOL CQFilePro::PreLoad(const CString& strPath)
    {
        boost::shared_array<BYTE> temp = boost::shared_array<BYTE>(new BYTE[PRE_LOAD_BUFFER_LENGTH]);
        int nReadLength;
        try
        {
            CFile file;
            if (file.Open(strPath, CFile::modeRead) == FALSE)
            {
                return FALSE;
            }
            do 
            {
                nReadLength = file.Read(temp.get(), PRE_LOAD_BUFFER_LENGTH);
            } while (nReadLength == PRE_LOAD_BUFFER_LENGTH);
        file.Close();
        }
        catch(...)
        {

        }
        return TRUE;
         }

My question is what is the difference between first open and second open. How can I accelerate the sqlite open-process.