Informix Ontape Backup Runs Slow

Question & Answer

Question

Backups of an Informix database using their "Ontape" utility runs very slow. There is a known performance issue in the Ontape utility that was fixed in Version 7.31.UC7; however the fix is NOT enabled by default.

Answer

Environment

All 7.3 and 9.x versions of Informix on all operating systems. Following is analysis/fix information from Informix:

BUG:
101062 ARCHIVE PERFORMANCE DEGRADATION WHEN MANY CALLS TO ARC_VERY_OLD_PAGE()

ANALYSIS:
Run onstat -g ath |grep arcbackup. You will find on 7.3x/9.x an arcbackup1 and arcbackup2 thread. Get the thread id of the arcbackup1 thread and then run the following command:

onstat -g stk tid

The tid is the thread id. Run this command several times during the archive. You will see many stacks that show the arc_very_old_pages function.

FIX:
The fix was in General Release 7.31.UC7 and higher and is turned off by default. The new functionality introduced by the fix to Bug 101062 is not turned on by default. You must enable the new functionality by setting the following ONCONFIG parameter before bringing the engine online.

  CCFLAGS 0x400000

To verify that the proper CCFLAGS settings are in effect:

Using dbaccess, select database 'sysmaster'. Run the following query:

  select hex(value) from sysshmhdr where name = "ccflags";

This will return:

(expression) 0x00400000

NOTE: This assumes you don't currently run with any other CCFLAGS enabled. You should also consider the following questions:

Do I need to perform level 0 backup right after turning on CCFLAGS?
Yes, When you enable CCFLAGS you need to take an archive after turning the same on. Then the fix to Bug 101062 will be in effect, and you can verify the same by monitoring that the arc_very_old_page function will not be seen on the arcbackup threads.
If I disable CCFLAGS are there any issues I need to be aware of?
When you disable CCFLAGS for 101062, the first archive after the flags have been disabled will be an invalid archive, and you will have to do 2 back-to-back archives.

[{"Product":{"code":"SWG10","label":"AIX"},"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Component":"Database management","Platform":[{"code":"PF002","label":"AIX"}],"Version":"5.3;5.2;5.1;4.3","Edition":"","Line of Business":{"code":"LOB08","label":"Cognitive Systems"}},{"Product":{"code":"SWG10","label":"AIX"},"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Component":"Installation- backup- restore","Platform":[{"code":"","label":""}],"Version":"","Edition":"","Line of Business":{"code":"LOB08","label":"Cognitive Systems"}}]

Historical Number

isg1pTechnote0303

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Document Information

Modified date:
17 June 2018

UID

isg3T1000184

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