INFORMIX SERVER / 5725A3900 / E10 - 

When running onmode -c block or using the API (as below) on an
RSS:

echo "execute function task ('checkpoint','block');" | dbaccess
sysadmin

The instance may fail to fully block, leaving the instance
unable to be unblocked via onmode -c unblock or the api
equivalent:

echo "execute function task ('checkpoint','unblock');" |
dbaccess sysadmin

The main symptoms are:

1, The online.log does not report "Dynamic Server Blocked" as
would be expected.

Below is from a successful block:

11:14:06  SCHAPI: Issued Task() or Admin() command "task(
'checkpoint', 'block' )".
11:14:06  SCHAPI: Issued command "onmode". This is the only
record of the command issuance.
11:14:09  Logical Log 4712 Complete, timestamp: 0x16123736.
11:14:09  Staging of logical logs successfully started.
11:14:09  Checkpoint Completed:  duration was 0 seconds.
11:14:09  Fri Sep 24 - loguniq 4713, logpos 0x7c1018, timestamp:
0x16129efc Interval: 21098

11:14:09  Maximum server connections 1
11:14:09  Checkpoint Statistics - Avg. Txn Block Time 0.000, #
Txns blocked 0, Plog used 151, Llog used 0

11:14:10  The external backup is blocking the database server at
checkpoint 4713:0x7c1018.
11:14:10  External Backup preparation complete - Time 3.027
11:14:10  Dynamic Server blocked.

2. The mreplay thread remains in the following cond wait state:

 115      4ac62368         45e8a9e8         3    cond wait
RESUME_app   8cpu         mreplay

****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 14.10.xC7.                 *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 14.10.xC7.                        *
****************************************************************

Reducing the number of OFF_RECVRY_THREADS to lower values may
reduce the occurrence, but this has to be considered in
conjunction with:
VPCLASS cpu,num=N
SEC_APPLY_POLLTIME=N - this should be 100 or lower but testing
should be performed to ensure Log Replay Apply performance is
not deteriorated
OFF_RECVRY_THREADS N - this should be lowered to values between
10 and 20 but testing should be performed to ensure performance
is not deteriorated

****************************************************************
* USERS AFFECTED:                                              *
* Users of Informix Server prior to 14.10.xC7.                 *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* See Error Description                                        *
****************************************************************
* RECOMMENDATION:                                              *
* Upgrade to Informix Server 14.10.xC7.                        *
****************************************************************

Fixed in Informix Server 14.10.xC7.

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

27.09.2021
02.11.2021
02.11.2021