AWR

Do AWR Reports Show the Whole Picture?

AWR report is a great source of aggregated information on top activities happening in our databases. I use data collected in AWR quite often, and obviously the easiest way of getting the data out from the AWR is by running the AWR report. In most cases that’s not an issue, but there are certain scenarios when…

Do you have enough Redo?

The question of whether a database has enough redo logs available is quite common. The documentation suggests to use FAST_START_MTTR_TARGET and V$INSTANCE_RECOVERY.OPTIMAL_LOGFILE_SIZE to identify “the optimal” redo log size based on the target recovery time. I’ve never used it and can’t comment if it is a correct/reasonable way or not. The easiest way to identify…

Meaning of “Disk Reads” Values in DBA_HIST_SQLSTAT

This post relates to my previous writing on mining the AWR. I noticed that it’s very easy to misinterpret the DISK_READS_TOTAL and DISK_READS_DELTA columns in DBA_HIST_SQLSTAT. Let’s see what the documentation says: DISK_READS_TOTAL – Cumulative number of disk reads for this child cursor DISK_READS_DELTA – Delta number of disk reads for this child cursor You…