???????????I/O?????????????????(large percentage of time waiting for disk I/O)

????????????I/O????:large physical I/O rate(not sufficient in itself)

 

??????????????????(low buffer cache hit ratio(not sufficient in itself))

????????????н?????У???CPU?????(large run queue with idle CPU)

 

????4.????????????

 

????SQL Server?????

 

????1 SQLServer?????????????????(Cache Hit Ratio)??????????á????????????80%?????????????檔


????2 ???Full Scans/sec(??????/??)??????????????1??2?????????????????????????????????裬???SQL???????????????

 

????3 Number of Deadlocks/sec(??????????/??)??????????ó??????????????к????????????????????顣?ü?????????????0??

????4 Lock Requests/sec(??????/??)????????????????????????????????ü??????????

 

????Oracle?????


????1 ??????????????0????????????????????????С??0.90????????????SHARED_POOL_SIZE???С??


???????(????SQL??)???????????????????

????select(sum(pins-reloads))/sum(pins) from v$librarycache;


????select(sum(gets-getmisses))/sum(gets) from v$rowcache;

 

??????????棺 select * from v$sgastat where name=??free memory??;


????2 ?????????????????С??0.90???????????DB_BLOCK_BUFFERS???????(??λ????)??

????????????????????????


????select name??value from v$sysstat where name in (??db block gets????

??????consistent gets??????physical reads??) ;


????Hit Ratio = 1-(physical reads / ( db block gets + consistent gets))


????3 ???????????????????????????LOG_BUFFER?????????

?????????????????????? ??

 

????select name??value from v$sysstat where name = ??redo log space requests?? ;

????4 ????????????????С??0.95????????SORT_AREA_SIZE???????????? ??

 

????????????????? ??

 

????select round((100*b.value)/decode((a.value+b.value)?? 0?? 1?? (a.value+b.value))?? 2)from v$sysstat a?? v$sysstat b where a.name=??sorts (disk)?? and b.name=??sorts (memory)??