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Informix - Problem description

Problem IT37242 Status: Closed

WITH DBSPACES COMPRISED OF MANY CHUNKS, FREQUENT 'CHUNK DOWN' CHECKING CAN
BE VERY EXPENSIVE

product:
INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10
Problem description:
On a secondary server system having multiple dbspaces with a
couple hundreds of chunks each, a significant log apply slowness
can be observed during heavy load on primary that, esp. with
HDR, can affect primary performance too.

Here's how this looks in 'onstat -g laq':

Log Apply Info:
Thread         Queue    Total      Avg
                Size   Queued    Depth
wreplay_1           0   189676     1.35
wreplay_2           0   153139     1.34
wreplay_3           0   260041     1.48
wreplay_4           0   161107     1.32
wreplay_5           0   164985     1.33
wreplay_6           0   115743     1.17
wreplay_7           0   246979     0.42
wreplay_8           0   172274     1.36
wreplay_9           0   125461     1.29
wreplay_10          0   116958     1.20
wreplay_11          0   211963     1.64

Secondary Apply Queue:         Total Buffers:48 Size:2048K Free
Buffers:0
Log Recovery Queue:            Total Buffers:48 Size:20480K Free
Buffers:0
Log Page Queue:                Total Buffers:1024 Size:2K Free
Buffers:0
Log Record Queue:              Total Buffers:1000 Size:16K Free
Buffers:981


So worker threads' queues empty or nearly empty most of the time
while Secondary Apply Queue, Log Recovery Queue and Log Page
Queue completely full, yet Log Record Queue again hardly used,
indicating a bottleneck at extracting log records from log pages
which is the bld_logrecs thread's business.

Looking at bld_logrecs thread under such conditions, that thread
would appear 'running' most of the time.
Problem Summary:
****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 12.10.xC15 and 14.10.xC7.  *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 12.10.xC15 or 14.10.xC7 (when     *
* available).                                                  *
****************************************************************
Local Fix:
Solution
Workaround
****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 12.10.xC15 and 14.10.xC7.  *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 12.10.xC15 or 14.10.xC7 (when     *
* available).                                                  *
****************************************************************
Comment
Fixed in Informix Server 12.10.xC15 and 14.10.xC7.
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
14.06.2021
31.08.2021
31.08.2021
Problem solved at the following versions (IBM BugInfos)
Problem solved according to the fixlist(s) of the following version(s)