??
??blog?????oracle????????????,??????????????,??????: ?????????. ???????: ??????????,????????; ????????????,?” ???”??.
1. OS swapping/paging ??????concurrency???????
Oracle?????????, ??latch/mutex???????”?”,??????????????/???(????????????,??????????????????). ????OS??????swapping/paging????,???????????,??latch/mutex???????,????????????hung/slow???.
??swapping/paging??????:
a). ????
b). ??????; ?????, ??????????????
c). ?????/????? ?????????????????
???????:
Lock SGA, ??SGA(???latch/mutex)???pin???????swapping???.
???SGA??????,????large page(hugepage)??,??latch/mutex??/?????.
2. SGA resizing??????????
?AMM/ASMM??????????, shared pool?buffer cache?????component????????????,??ora-4031???.??????????,???????resize????????????(?latch/mutex?????)?????, ?????????latch/mutex??. ????shared pool?resize??????,??latch/mutex???????.
?????????:
?????bug; ???????????,??resize???????????????,???????????. ??bug?fix??????????impact, ???????????.
???????:
1). ??buffer cache?shared pool??(???????????,?????????)
2). ??resize???????16??
alter system set "_memory_broker_stat_interval"=999;
Disable AMM/ASMM?????????,?????: ??ora-4031????????????.
3. DDL??????????
??????????????????.
???????????DDL (??grant, ?????, ????????),???????????SQL?????invalidate?;????????SQL????????????,?????????hard parse ? SQL??????. ??????? “hardparse storm”, latch/mutex????????, ??library cache lock/row cache lock????; ??????????slow/hung.
???????:
???????????DDL
??????????,???????????,?? “????????????3?????"?
