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High avg wait time log file sync

AndreHXDec 21 2017 — edited Dec 29 2017

Hello,

we migrated from a 12.1.0.1 standard edition without asm and sles 11 to an 12.2.0.1 enterprise edition with asm, sles 12 and SSD for Data and Redolog.

After that we have on high workload times a log file sync avg wait about 50ms.

From the AWR:

Begin Snap:425720-Dez-17 09:00:12317  54.7
End Snap:426220-Dez-17 14:00:25261  58.9

Top 10 Foreground Events by Total Wait Time

EventWaitsTotal Wait Time (sec)Avg Wait% DB timeWait Class
DB CPU 38.1K 52.1
log file sync548,57130.8K56.15ms42.1Commit
direct path read6,117,6911978323.33us2.7User I/O
db file sequential read4,253,0081731.8407.20us2.4

User I/O

Most of the time the wait time is ok but there a about 1% with more than 32ms

EventWaits 1ms to 32ms <512us <1ms <2ms <4ms<8ms<16ms<32ms>=32ms
log file sync496K8.759.423.06.21.8.1.0.9

% of Total Waits
EventWaits 4s to 2m<2s <4s <8s<16s<32s< 1m< 2m>=2m
log file sync438899.2.1.4.3

I think the log file parallel write is ok, so it is no I/O related issue:

EventWaits%Time -outsTotal Wait Time (s)Avg waitWaits /txn% bg time
log file parallel write841,23901,1421.36ms1.5630.30

We increased the cpu priority of the lgwr processes, but it does not help.

Do you have any suggestions?

Thanks

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Added on Dec 21 2017
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