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Informix - Problem description

Problem IT40074 Status: Closed

MISSING READ-AHEAD IN RSS UNDERGOING LOGICAL LOG RESTORE

product:
INFORMIX SERVER / 5725A3900 / E10 - 
Problem description:
An RSS having to receive logical logs from log restore rather
than from primary might perform poorly due to missing
read-ahead.

Reason is an RSS read-ahead optimization moving the read-ahead
from bld_logrecs thread to RSS_Recv thread which, during log
restore, is in wait state, so would not see any log records and
not submit any read-ahead requests.

You can verify non-existing read-ahead be 'onstat -g rah'
returning empty read-ahead statistics.
Problem Summary:
****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 14.10.xC8.                 *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 14.10.xC8.                        *
****************************************************************
Local Fix:
Workaround, for the duration of the log restore:

 onmode -wf CDR_FEATURES NORAOPT

After log restore completed, when logs are being received from
primary, re-enable the optimization using

 onmode -wf CDR_FEATURES RAOPT
Solution
Workaround
****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 14.10.xC8.                 *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 14.10.xC8.                        *
****************************************************************
Comment
Fixed in Informix Server 14.10.xC8.
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
25.02.2022
08.04.2022
08.04.2022
Problem solved at the following versions (IBM BugInfos)
Problem solved according to the fixlist(s) of the following version(s)