Wait V$ Views

Question

Hi Guys
Please suggest me from which V$ View i can get the max cpu utilized, CPU Wait time, CPU Wait, cause for CPU wait, latch wait in library cache, latch free.
Kindly help me Guys...
Thanks
Ram

Answer 1

In V$SYSSTAT and V$SESSTAT you can find the CPU related information ('CPU used when call started','CPU used by this session')
With V$OSSTAT and DBA_CPU_USAGE_STATISTICS you can find the OS level how all the CPU's being used.
In Oracle, the majority of wait time is spent waiting in I/O or performing computations. As we have stressed, CPU enqueues can be observed when the CPU run queue exceeds the number of CPUs on the database server, and this can be seen by looking at the “r” column in the vmstat UNIX/Linux utility or within the Windows performance manager.
If the system is already optimized, having CPU time as a top wait event is a positive because the addition of faster CPUs or more CPUs will relieve the bottleneck.
However, high CPU usage is also indicative of excessive logical I/O (consistent gets ) against the data buffers which might indicate the need for SQL tuning or shared pool and library cache tuning. High CPU usage will be reported as a top 5 timed even in any AWR report as shown below:
Top 5 Timed Events
% Total
Event Waits Time (s) Ela Time
CPU time 4,851 4,042 55.76
db file sequential read 1,968 1,997 27.55
log file sync 299,097 369 5.08
db file scattered read 53,031 330 4.55
log file parallel write 302,680 190 2.62