Expert Advice

Free_Space_in_zFS_User_Cache  
Situation Description
Suggested Actions
Situation Description

Free Space in the zFS User Cache has dropped below 5,000 pages. The zFS user file cache is used to cache all "regular" files. It caches any file, of any size, and performs write-behind and asynchronous read-ahead for files. The zFS user file cache performs I/O for all files that are 7K or larger.

 

Suggested Actions

The User Cache is allocated in data spaces. Its default size is 256MB. The maximum size is 65,536MB (64GB). The Free_Space_In_zFS_User_Cache Situation monitors the number of available free pages in the cache. You can use the MVS modify command (F zfs,query,{…}) to verify if the situation is accompanied by a low hit ratio (less than 80%). If this happens frequently, you may want to increase the value of the user_cache_size configuration parameter.

 

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