A skewed index has many records clumped close together on the index tree due to their similar indexed values. When an index is skewed, parts of an index are accessed more frequently than others. As a result, disk contention may occur, creating a bottleneck in performance.This is a tricky question for every DBA.
Retrieve Stats for a Day from Statspack tables
select to_char ( trunc ( b.snap_time ) , 'DD-MM-YYYY' ) , statistic# , name , sum ( value ) from STATS$SYSSTAT A , stats$snapshot B where a.snap_id = b.snap_id and trunc ( b.snap_time ) > trunc ( sysdate - 30 ) and a.statistic# = 54 < Replace with Stats Number Below > group by trunc ( b.snap_time ) , statistic# , name order by trunc ( b.snap_time );
1. Look at table PERFSTST.STATS$SNAPSHOT
2. Run spreport.sql and you will notice it along with the snapids listed
This process will reverse database roles in a Data Guard setup, i.e. standby database becomes primary.
Solution: I tried looking into statspack report but it wouldn’t flag the insert/update/delete activity. Also statspack won’t record some of system activity which may contribute to redo logs.Only option to use was “LOGMINER”.
I have a SAP system with optimizer_index_cost_adj set to 10. Let’s look at Oracle execution plans and the resulting execution costs.
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