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Summary: in the Oracle database, you can often see a special wait event: Sync ASM rebalance. The basic meaning of this wait event is to synchronize ASM rebalancing changes in a cluster so that ASM changes can be consistent across clusters.

In Oracle databases, you can often see a special wait event: Sync ASM rebalance.

The basic meaning of this wait event is to synchronize ASM rebalancing changes in a cluster so that ASM changes can be consistent across clusters.

This event comes from an enhancement in 11g, and in 10g, the following BUG reveals the problem caused by the failure of ASM Rebalance information to synchronize globally:

Bug 4430246 ASM Disk expel (after a rebalance) is not synchronous cluster-wide

However, in Oracle 12.2 and 18c, the occurrence of this event has nothing to do with the Rebalance of the disk, but is caused by some BUG, such as:

EM13c Space Monitoring Query (sqlid=69p6my4hpdm3j) On dba_tablespace_usage_metrics Timed Out after Db Upgraded To 12.2 (Doc ID 2375714.1) Bug 26928317 SAGEASM-E ASM hang at 'sync asm rebalance' with underlying corruption

In response to these situations, the official temporary solutions are:

Alter system set "_ use_cached_asm_free_space" = TRUE scope=spfile

When you encounter this situation, please contact your technical support partner.

The following is an AWR instance with the highest proportion of Sync ASM rebalance wait events:

Event Waits Total Wait Time (sec) Avg Wait% DB time Wait ClassSync ASM rebalance 10997 470.3 42.77ms 20.6 Other log file sync 5503 172.3 31.31ms 7.6 Commitcontrol file sequential read 43966 114.1 2.60ms 5.0System I/Oenq: IV-contention 95614 72.1 753.93us 3.2Other

The above is for reference only.

For more analysis of Oracle cases, please stamp: https://www.modb.pro/u/368?cyn

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