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Informix - Problem description

Problem IT36873 Status: Closed

IN-PLACE ALTER TABLE CAN LEAD TO A FLOOD OF PAGE OUT-OF-SEQ ERRORS IN
ONLINE.LOG WHEN USING CDC

product:
INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10
Problem description:
The following was reported on linux x86-64 running IDS
12.10.FC12 and reproduced on same.

This problem can happen on a table that is being captured by CDC
and it has been altered and now has a
couple page versions (confirmed by oncheck -pT).

If you stop CDC full row logging, do an in-place alter on the
table, start CDC full row logging and
then do a small update on the table, you may see a flood of
errors to the online.log that look like:

12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a4,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a5,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a5,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a6,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a6,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a7,
cur page 6:b1]
12:28:05  CDC: Log Seq:  Page out-of-seq error [got page 6:61a7,
cur page 6:b1]

When this starts happening, you will also see a couple dbWorker
threads start using a lot
of cpu as it looks like they get extremely busy processing the
ph_dbs_alert task.

Even when the out-of-seq errors stop being reported, the
dbWorker threads will
remain using high cpu for quite a while.

It seems like you can workaround this problem by resolving the
in-place alter table
before turning full row logging back on.
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).                                                  *
****************************************************************
The correct call sequence is:

cdc_endcapture()
cdc_set_fullrowlogging(DISABLE)
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).                                                  *
****************************************************************
The correct call sequence is:

cdc_endcapture()
cdc_set_fullrowlogging(DISABLE)


Comment


Fixed in Informix Server 12.10.xC15 and 14.10.xC7.


Timestamps


Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

12.05.2021
23.08.2021
23.08.2021


Problem solved at the following versions (IBM BugInfos)




Problem solved according to the fixlist(s) of the following version(s)