Peter,

Yes, some confusion was caused by terminology: I regard VLF as the manager of 
the cache and the exploiters as doing 'caching', meaning giving an object to 
VLF to put it in its cache.

Finally, the first and basic question of this thread was: 
-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?
Besides all the information you do not wish to publish, this in my opinion is 
useful information worth publishing.

Kees.


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of Peter Relson
Sent: 30 November, 2014 16:58
To: [email protected]
Subject: Re: VLF caching

>Now, please put your wisdom in IBM books.

I think that most of my post was discussing internal details that are not 
suitable for documentation (where by documenting them, customers and 
programmers are allowed to rely on them, which in turn may hamstring future 
desire to change). If there are particular pieces that would really help 
customers if we document them, I'll listen to requests for them (which should 
include at least a hint of how it will help). 

>>If LLA finds that a module that it had successfully gotten cached no 
>>longer is deemed worthwhile, it does not tell VLF.

>No?  Why?

Not having been involved in the initial implementation, I'm not sure. 
Perhaps it was felt that doing so would be overkill, that trimming would do a 
good enough job such that the overhead of doing the "delminor" was not worth 
the cycles. It also makes it less flexible -- if there are subsequent fetches, 
LLA might be able simply to mark its data as "active" 
and not have to re-cache the module. 

Peter Relson
z/OS Core Technology Design

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