formula to calculate log buffer

[pando]

Hi

I came across with this formula to calculate an aproximate value for log buffer from Anjo Kolk´s YAPP whitepaper


(3* ( (redo size/(user commits + user rollbacks)) * transaction commits per second))/2

I can get all the values except transaction commits per second, I took the value from user commits per second but the value calculate is like 5000 bytes, doesnt look right to me or I am taking the wrong value?

Note: Multiply by 1.5 since LGWR will start to write the redo buffer when it becomes 2/3 full or when a foreground or DBWR will post LGWR.

[pnrdba]

Hi pando,
I think there is a way to find out the transaction commits per second.
Go to v$system_event and do the following:
SQL> col event format a40
SQL> col event format a40 tru
SQL> select * from v$system_event;

EVENT TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED AVERAGE_WAIT TIME_WA
---------------------------------------- ----------- -------------- ----------- ------------ -------
log file sync 30103 86 97242 3

You can take the statistics over a period of time and then divide it to get transaction commits per second.

Correct me if i'm wrong.

Thanks

PNRDBA