How does Spotlight calculate SGA size and Library Cache hit rate?
This is what I see in my cluster environment:
1) The sum of SGA size is incorrect. Here is how I calculated the SGA usage in GB. What I got is 7.06GB which is about right since we have sga_target=7216M. But the current SGA usage section on spotlight consistently shows that SGA current size is 9.21 GB.
1* select sum(value)/1024/1024/1024 from v$sga
SQL> /
SUM(VALUE)/1024/1024/1024
-------------------------
7.046875
2) Library Cache Miss Ratio Alarm sends out false alert.
The spotlights library cache hit ratio is very different from the following query we used to calculate library cache hit ratio.
SQL> select sum(pinhits)/sum(pins) from v$librarycache;
SUM(PINHITS)/SUM(PINS)
----------------------
.989544175
SQL>
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