Today i was preparing report like whats Average Archive generation on my DB's so that i can arrange arch dests accordingly.
While doing this i was pulling data from v$log_history for date wise archive files count that got generated.
I know this much that v$log_history pulls data from control file.
But interesting thing i found that on each DB the number of entries in v$log_history are different. What i meant is some had data for last 150+ days while some had till 100 days only.
I mean its not a problem for me but Why is it like this?
My guess is Oracle internally manages control file and over writes/deletes data which is not needed as per the load activity on that DB to accomodate new data.
One thought also touched my mind is concept of "resetlogs opening of DB" but doesnt apply here as all the DB i checked are Prod DB's and they are in no way opened with resetlogs in last 1 yr or 2yr.
Anybody want to through light on this ??????
ok i searched on metalink with different terms and i got this...
Doc ID: 1060139.6
How to Clean-Up Entries in V$LOG_HISTORY and/or V$ARCHIVED_LOG:
The number of archived redo log files maintained in the controlfile and
available through V$LOG_HISTORY is determined by the MAXLOGHISTORY parameter of
the create database command. The archived redo log records are maintained up to
the value of MAXLOGHISTORY, then wraps and overwrites any previous entries starting
from the beginning.
That explains it . thought might be usefull for somebody...
Data stored in v$log_history table depends on maxloghistory parameter of controlfile. This parameter set during database creation or controlfile re-creation. Means if data would be more than it will overwrite and if you want to change value of same parameter and want to store more data in v$log_history then you should need to re-create controlfile.
Thanks and regards,
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