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High "enq: SQ - contention" waits in RAC (Doc ID 2156730.1)

Last updated on MARCH 05, 2023

Applies to:

Oracle Database - Enterprise Edition - Version and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.


RAC databases are performing slowly due to heavy "enq: SQ - contention" waits.

AWR and ASH reports show that "enq: SQ - contention" is the top wait.

The following is an example from the AWR report:

Top 10 Foreground Events by Total Wait Time

Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class
enq: SQ - contention 10,690,523 46.2K 4 63.9 Configuration
DB CPU 11.8K 16.3
enq: TX - index contention 439,578 9004.6 20 12.5 Concurrency
buffer busy waits 1,104,082 1507.4 1 2.1 Concurrency
db file sequential read 1,122,853 1419.5 1 2.0 User I/O
db file scattered read 29,548 779.6 26 1.1 User I/O
library cache: mutex X 2,242,811 769.2 0 1.1 Concurrency
latch: ges resource hash list 529,983 412 1 .6 Other
cursor: pin S 933,128 227 0 .3 Concurrency
direct path read 99,101 186.9 2 .3 User I/O



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