Re: Redo log size on a 4 node RAC cluster.

Zabair,

From the AWR reports, determine peak redo rates ..

redo log size >= peak redo rate / minute x 20 minutes

You can get more information either from the documentation or the Redo Apply & Media white paper published by Oracle Corp.

Rajeev
> On Aug 23, 2017, at 6:58 AM, Zabair Ahmed (Redacted sender "roon987" for DMARC) <dmarc-noreply_at_freelists.org> wrote:
>
> Hello,
>
> 11.2.0.4 EE on 4 node RAC Redhat 6.6 Cluster.
>
>
> We are constantly seeing "Checkpoint not complete" message in the alert log:
>
> Thread 2 cannot allocate new log, sequence 109658
> Checkpoint not complete
> Current log# 26 seq# 109657 mem# 0: +ARCH01/prd/onlinelog/group_26.393.904013409
> Current log# 26 seq# 109657 mem# 1: +ARCH01/prd/onlinelog/group_26.634.904013411
> Thread 2 advanced to log sequence 109658 (LGWR switch)
> Tue Aug 22 00:03:06 2017
> LNS: Standby redo logfile selected for thread 2 sequence 109658 for destination LOG_ARCHIVE_DEST_2
> Current log# 3 seq# 109658 mem# 0: +ARCH01/prd/onlinelog/group_3.263.877611157
> Current log# 3 seq# 109658 mem# 1: +ARCH01/prd/onlinelog/group_3.273.877680615
> Tue Aug 22 00:03:11 2017
> Archived Log entry 510017 added for thread 2 sequence 109657 ID 0x1b7b9f46 dest 1:
> Tue Aug 22 00:11:39 2017
> Thread 2 cannot allocate new log, sequence 109659
> Checkpoint not complete
> Current log# 3 seq# 109658 mem# 0: +ARCH01/prd/onlinelog/group_3.263.877611157
> Current log# 3 seq# 109658 mem# 1: +ARCH01/prd/onlinelog/group_3.273.877680615
> Thread 2 advanced to log sequence 109659 (LGWR switch)
> Current log# 22 seq# 109659 mem# 0: +ARCH01/prd/onlinelog/group_22.744.904009995
> Current log# 22 seq# 109659 mem# 1: +ARCH01/prd/onlinelog/group_22.931.904009999
> Tue Aug 22 00:11:44 2017
> LNS: Standby redo logfile selected for thread 2 sequence 109659 for destination LOG_ARCHIVE_DEST_2
> Tue Aug 22 00:11:50 2017
> Archived Log entry 510019 added for thread 2 sequence 109658 ID 0x1b7b9f46 dest 1:
> Tue Aug 22 00:21:55 2017
> Thread 2 cannot allocate new log, sequence 109660
> Checkpoint not complete
> Current log# 22 seq# 109659 mem# 0: +ARCH01/prd/onlinelog/group_22.744.904009995
> Current log# 22 seq# 109659 mem# 1: +ARCH01/prd/onlinelog/group_22.931.904009999
> Thread 2 advanced to log sequence 109660 (LGWR switch)
> Current log# 4 seq# 109660 mem# 0: +ARCH01/prd/onlinelog/group_4.265.877611161
> Current log# 4 seq# 109660 mem# 1: +ARCH01/prd/onlinelog/group_4.274.877680623
> Tue Aug 22 00:22:00 2017
> LNS: Standby redo logfile selected for thread 2 sequence 109660 for destination LOG_ARCHIVE_DEST_2
> Tue Aug 22 00:22:09 2017
> Archived Log entry 510026 added for thread 2 sequence 109659 ID 0x1b7b9f46 dest 1:
> Tue Aug 22 00:30:36 2017
> Thread 2 cannot allocate new log, sequence 109661
> Checkpoint not complete
> Current log# 4 seq#
>
> Also ASH Report listing "log file switch (checkpoint incomplete)" as the Top User Event.
>
> All this is indicating that we have redo logs which are incorrectly sized.
>
> My question is how do you determine the correct redo log size? Currently the redo log size 1.5GG in all 4 instances.
>
> Can you mix and match different redo log size for different instances? Is this recommended? We are getting the "Checkpoint not complete" message only on Instance 2!
>
> Are there any disadvantages in having different redo log sizes for different instances? Do other people do this? Or should we keep the redo log size the same across all 4 instances?
>
> We are also running this in a DataGuard environment.
>
> Appreciate any feedback.
>
> Thanks
>
>

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