A fix is available
APAR status
Closed as program error.
Error description
Additional Symptom(s) Search Keyword(s):Queue Manager hangs during log processing Change Team finds that a channel needs to write a log record during MQPUT processing and CSQJW001 has detected that all of the log buffers are full so it must kick start the log-writer. However, the log RBA passed by CSQJW001 in LRB7RBA8 is calculated incorrectly due to the small size of the log buffer defined on the queue-manager (ie. OUTBUFF being set to the smallest value allowed). This results in CSQJW001 continually trying to kick start the log writer for an RBA that has already been written, hence no further log buffers are freed up.
Local fix
Code OUTBUFF to at least 80
Problem summary
**************************************************************** * USERS AFFECTED: All users of WebSphere MQ for z/OS Version 8 * * Release 0 Modification 0. * **************************************************************** * PROBLEM DESCRIPTION: When CSQ6LOGP is compiled with OUTBUF < * * 68, the queue manager hangs if all * * available log buffers are filled while * * writing a log record to the queue * * manager logs. High CPU usage can be * * observed in the queue manager address * * space, and in some cases the address * * space of the application waiting for a * * log record to be written. * **************************************************************** * RECOMMENDATION: * **************************************************************** While attempting to write a log record to the queue manager recovery logs, CSQJW001 detected that no log buffers were available. CSQJW001 resumes the log writer task to write out the contents of the log buffers up to a specified RBA, freeing up those buffers for reuse. The RBA specified must be prior than the RBA of the last complete log record written to the logs and so to ensure this is always the case, an RBA 17 control intervals prior to the current RBA is passed. However when OUTBUF is less than 68, the passed RBA has already been written out and the log writer returns immediately - no log buffers are written out and so CSQJW001 detects that there are still no available log buffers and resumes the log writer task again, passing the same RBA, and the log writer again completes without writing out any buffers. This repeats indefinitely, leading to high cpu in the queue manager address space, and the address space writing out the log record. Other tasks/applications attempting to write log records while this is occurring will suspend on the log writer latch.
Problem conclusion
The minimum value of OUTBUFF is increase to 80, requiring up to 40K of additional private storage. This ensures the RBA required to be passed to the log writer task is always within the scope of the log buffer. To maintain compatibility, values of OUTBUFF less than 80 will be accepted, and will be treated internally as if a value of 80 had been specified. The following page in the WebSphere MQ 8.0.0 Knowledge Center is updated: IBM MQ Configuring Configuring queue managers on z/OS Custominsing IBM MQ Task 17: Tailor your system parameter module Using CSQ6LOGP (q019310_.htm) The description of OUTBUFF is changed from "The parameter must be in the range 40 through 4000. The value specified is rounded up to a multiple of 4. " to "The parameter must be in the range 80 through 4000. The value specified is rounded up to a multiple of 4. Values between 40 and 80 will be accepted for compatibility reasons, and will be treated as a value of 80." 000Y CSQJS001
Temporary fix
********* * HIPER * *********
Comments
APAR Information
APAR number
PI56807
Reported component name
WMQ Z/OS 8
Reported component ID
5655W9700
Reported release
000
Status
CLOSED PER
PE
NoPE
HIPER
YesHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2016-02-08
Closed date
2016-03-24
Last modified date
2016-06-02
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UI36474
Modules/Macros
CSQJS001
Fix information
Fixed component name
WMQ Z/OS 8
Fixed component ID
5655W9700
Applicable component levels
R000 PSY UI36474
UP16/05/04 P F605 ¢
Fix is available
Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.
[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"8.0","Edition":"","Line of Business":{"code":"LOB45","label":"Automation"}}]
Document Information
Modified date:
02 June 2016