Latch: Row Cache Objects Contention with Parallel Hints on dc_rollback_segments
(Doc ID 2254222.1)
Last updated on AUGUST 04, 2018
Applies to:Oracle Database - Enterprise Edition - Version 22.214.171.124 to 126.96.36.199 [Release 11.2]
Information in this document applies to any platform.
- High "latch: row cache objects" event contention observed when executing query with parallel hints.
- This issue may be reported when using Parallelism in the Select Clause and CTAS Queries with PARALLEL Hints
- Contention seen on the "latch: row cache objects" wait event and high gets on the dc_rollback_segments rowcache together with ktuGetUsegDba() involved in the waiting session stacks.
Call Stack of Waiting Session:
- Issue effects Database version 188.8.131.52,184.108.40.206 and 220.127.116.11
- An AWR report may look similar to the following:
Top 10 Foreground Events by Total Wait Time
Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class
DB CPU 2156.8 94.3
latch: row cache objects 2,806,811 132.7 0 5.8 Concurrency
Dictionary Cache Stats
Cache Get Requests Pct Miss Scan Reqs Pct Miss Mod Reqs Final Usage
dc_rollback_segments 55,797,787 0.00 0 0 3,029
Database Upgrade to 18.104.22.168.0, 11,2.3.0 or 22.214.171.124
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