Hi Mike, >> Mike Baker <[EMAIL PROTECTED]> wrote: If we have lots of >> redundant datasets on the machine, and many HLQ (high level qualifiers) >> which could (also) be completely removed, but have not been removed / >> cleaned up, is this likely to have much of a performance degradation >> affect on the Catalog / CAS.
Mike, I'm not certain I fully understand the description of your situation. For example, how many is "lots", and what exactly is a "redundant dataset"? Nevertheless, however I interpret the situation, my opinion is that it does not affect the performance of either the catalog or CAS. The catalog is physically a VSAM KSDS, accessed directly by key, and even if it contains thousands (even tens of thousands) of useless records, the speed of access to any record in the catalog will not be affected by the "redundant" records. Most (possibly all) of the catalog's index will/should be in CAS buffers, and therefore, accessing any record in the catalog's data component will require just a single I/O (at most). The same answer applies to CAS performance -- there's no way that redundant catalog records can affect CAS performance. Assuming by "redundant" data set you mean a cataloged data set that doesn't actually exist, this redundant record would never be read in the first place, and would never find its way into CAS. Since it would never be read, it wouldn't "take up space" in CAS buffers, as records are brought into CAS only by specific request when a task attempts to locate a data set. By your question, I'm guessing that you possibly believe all of a catalog's records are somehow buffered in CAS, regardless of being specifically requested, and that's not true. In my opinion, the single biggest performance benefit you can give your catalog(s) is to turn on VLF (the Virtual Lookaside Facility) within CAS (which is specified in the COVLFxx member of SYS1.PARMLIB, and can be checked by a MODIFY CATALOG,PREPORT,VLF operator command). This topic has been discussed many times on this Listserv, and can be found in the archives. There's also very good and extensive information on this in the z/OS DFSMS: Managing Catalog manual, SC26-7409. Having said that, cleaning up "redundant" data set records -- for example, entire HLQ levels of useless data set entries that haven't been cleaned up -- makes your catalog at risk of significantly greater problems when/if you have a catalog problem which requires diagnostic analysis. Any attempt to run diagnostics on this catalog will likely identify "lots" (your word) of useless records that just clutter up the true status of the catalog. By not cleaning up these entries, you're potentially creating a bigger problem for yourself at some later time -- and if that time is when you have an outage on the catalog and it results in longer recovery time, you may have critical applications delayed while you struggle with a "dirty" catalog. I hope I've shed some light on your question. If I'm on a tangent and don't understand what you're asking, drop me a note (on the Listserv, or privately). Ron Ferguson President and CEO Mainstar Software Corporation www.mainstar.com [EMAIL PROTECTED] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
