>-can I use VLF trimming statistics as a good measure to > determine if my CSVLLA cache is large enough? >-If not, what measure does tell me this, besides the > LLAFETCH/PGMFETCH measures I get from CSVLLIX1/2?
Provided by the VLF owner: Since LLA expects VLF to trim as needed to make room for new caching candidates over time, trimming itself is not a bad thing. What -is- bad is trimming 'too soon' so that you do not get as much benefit from caching a program object (module) as you otherwise might. As of z/OS 2.1, you can use the verbose output of the VLF Health Check to see the youngest age of a trimmed object (since the VLF class was activated), and the current minimum trimmed age of objects (since the check last ran) for the CSVLLA class. The output also shows the current MaxVirt value. You also can set an alert for a minimum age, so that the check will raise an exception if objects are being trimmed sooner than you would like (the default is 60 seconds - sufficient to tell whether there is a potentially serious issue). And you can dynamically change the size of the cache via the MODIFY VLF,REPLACE,NN=xx command by supplying a parmlib member with a new MaxVirt (and possibly AlertAge) parm for the CSVLLA class. I can not say whether there is some trimming statistic that would also be useful for older releases, but I doubt it. And the "modify" to change the size of the cache is available only as of z/OS 2.1 Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
