I assume most of you are familiar with the I/O adapters that have cache batteries on them and the importance of monitoring the status of those batteries to ensure they are replaced before they fail. In case you’re not: the IOA has a cache to improve performance; the application doesn’t have to wait for the data to be written to the disk. The cache is powered by a battery in the IOA to ensure the cache data is preserved even if the IOA is powered off or reset. However, if the cache battery is failing, then the data is written directly to disk and the cache isn’t used, which can result in significant performance degradation. As such, you should know when the cache batteries are failing to get them replaced before it affects your application’s performance.
Various ways to display the status of your cache batteries exist, including one very new method that we’ve recently made available via PTFs. I’m only going to briefly summarize the existing methods of checking the battery status, since I really want to share the new information.
The system is aware when the cache batteries start to fail, and sends message CPPEA13 to the QSYSOPR message queue. The first-level message text for this message is somewhat vague – “Contact your hardware service provider.” However, in the recovery section of the message it says you should have the cache battery replaced. When this message is sent to QSYSOPR, you’ll also have a problem created in the problem log, and you can use WRKPRB to display the problem details.
You can use the Work with Disk Status (WRKDSKSTS) command to determine if you have cache batteries requiring attention. Press F11 to get to the second panel; if the status for the disk unit is DEGRADED, it’s possible the issue is due to failing cache batteries. If your drives are mirrored, however, they’ll always show ACTIVE status and you must use one of the alternative ways to check the cache battery status.
There are a two different ways you can view your cache battery status using System Service Tools (STRSST):
1. You can use the Hardware Service Manager to work with resources containing cache battery packs, which will show you the resources that have cache batteries, and you can then display the battery information.
2. You can use the Display/Alter/Dump service function to invoke the batteryinfo Advanced Analysis feature to display the status of your cache batteries.
And now for the news: some recent PTFs (one for each supported release) now provide a simple program that you can call that to display the cache battery status. They are:
7.1 – SI40406
6.1 – SI40404
5.4 – SI40403
To display the cache battery information, simply run the following:
This will create a spool file containing the cache battery information for the IBM i partition where the function is run. To use this function you must have *SERVICE special authority, or be authorized to the Service Trace function. The Change Function Usage (CHGFCNUSG) command, with a function ID of QIBM_SERVICE_TRACE, can also be used to change the list of users that are allowed to perform this operation.
This blog post was originally published on IBMSystemsMag.com and is reproduced here by permission of IBM Systems Media.