Facing Many Blocking Session For Parallel Queries After 11gR2 Upgrade.
(Doc ID 1968169.1)
Last updated on FEBRUARY 27, 2019
Applies to:Oracle Database - Enterprise Edition - Version 184.108.40.206 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.
When a threshold is set for 'DBMS_SERVER_ALERT.BLOCKED_USERS' using server alert functionality, alerts are generated in 11.2 and up for situations where
a parallel query coordinator is waiting on parallel slaves to return results. These waits are cleared automatically.
You will see messages similar to 'Session XXXX is blocking 0 other sessions'.
Upgrade to 11.2.
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