MVS BOOT CAMP: Leveraging Your Coupling Facility to Enhance LOGREC

by John E. Johnston
October 1, 2004

There are many new and valuable functions and features in today’s mainframe environment. This article addresses one of these, the use of a coupling facility structure and the system logger to manage LOGREC data collection.

LOGREC data is comprised of records created when hardware or software errors are encountered. The data can be printed and analyzed using the Environmental Record Editing and Printing (EREP) program. Collecting LOGREC data has always been a bit cumbersome (not as onerous as collecting SMF data, but still a pain).

Old-Style LOGREC Data Collection
With the traditional LOGREC data collection method, the LOGREC data is stored on a disk data set. When the disk data set fills up, a console message is issued. When this “full” message is generated, either the computer operator or the mainframe automation software submits a batch process that copies the data to another storage area (usually a disk or tape Generation Data Group [GDG]), and then clears out the LOGREC data set. When multiple MVS images are deployed in a Parallel Sysplex environment, each MVS image must implement its own LOGREC data collection system.

The challenge is greater when you need to access this LOGREC data using the EREP program. Usually, where you need to run EREP, you’ll need to access the LOGREC data from multiple systems. With the traditional method, this means you must concatenate the appropriate LOGREC history data in your EREP JCL. While this is not an insurmountable ordeal, it’s just plain clumsy.

New-Style LOGREC Data Collection
In a Parallel Sysplex environment, you can leverage your coupling facility and the MVS logger component to automate LOGREC data collection. With this method, all the MVS images in your Sysplex write their LOGREC data to a structure in your coupling facility. When the structure fills up, the MVS logger function offloads the data into a disk data set. The MVS logger also prunes old records automatically based on parameters the systems programmer sets. Note: In a single system Sysplex, you can use a DASD-only log stream instead of a coupling facility structure.

Implementing LOGREC Data Collection
Implementing the new-style LOGREC data collection method requires that you:

•    Determine the size needed for the LOGREC structure
•    Create a new CFRM policy to add the LOGREC structure
•    Activate the new CFRM policy
•    Allocate the LOGREC log stream by updating the LOGR policy
•    Change the LOGREC recording medium to the log stream.

You can use two methods to determine the size needed for the LOGREC structure. IBM recommends that you determine how many records are written per second to the LOGREC data set on each of your systems, then use the CFSizer utility (www.ibm.com/servers/ eserver/zseries/pso) to determine the size.