There seems to be something missing from this discussion - namely that many (100's, 1000's?) of aliases can map to the same user catalog. There is an upper limit on the number of aliases (based I believe on max record size defined for the USERCAT), so you may need more than one; but there is no reason you couldn't, for example, put all 3rd party vendor datasets in one usercat. You may also want to map some data sets into separate usercats to allow different access control to the catalogs, or to keep the catalog from getting so large that it is difficult to ever move or recover if it gets damaged, or possibly to isolate production catalog information from test catalog information, etc., etc.
The division of dataset HLQ's among user catalogs is completely up to individual installations. The last thing I would want would be for some vendor to tell me how to do this, as our layout is based on our own installation standards and our Disaster Recovery procedures. For example, we have two USERCATs for the HLQ for in-house TSO users and I (as sysprog) have a TSO userid under each, so if we need to move one of those catalogs I can run under the other TSO userid while doing the move and not be impacted while the first catalog is unavailable. We isolate tape datasets to a separate catalog to simplify recovery issues with the Tape Management System database. Some other classes of "temporary" datasets that are deliberately not covered by DR are isolated to separate catalogs that can be wiped and rebuilt empty when the associated DASD pools are re-initialized empty. The one hard and fast rule though is to reserve the Master catalog for system data sets and alias pointers to USERCATs and deny update to the Master Cat to everyone except System Programmers, as an inappropriate change to Master Cat or a damaged Master Cat can give you a dead system. When you minimize the updates to the Master Cat, then it is not difficult to maintain backups of the Master Cat that are current enough to use for stand-alone restore in a worst-case scenario of unusable Master Cat. At our installation part of the management tasks associated with introducing datasets with a new HLQ into the system is to create a new RACF userid or group (required before a dataset profile can be created), create a new RACF generic dataset profile to guarantee all the datasets with that HLQ are protected by default, and define a new catalog alias to point to some appropriate pre-existing catalog. Joel C Ewing On 07/09/2010 02:27 PM, Charles Mills wrote: > Would people agree with the following? > > If a vendor were shipping a product that resided in two datasets, FOO.THIS > and FOO.THAT, best practice would be to recommend that the installer either > create a user catalog named FOO or a user catalog with an alias of FOO so > that the FOO.xxxx datasets would not take up space in the master catalog? > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf > Of Veilleux, Jon L > Sent: Friday, July 09, 2010 11:57 AM > To: [email protected] > Subject: Re: Dumb question on DEFINE ALIAS > > Short answer...to separate application files from the master catalog and to > keep the master catalog as small as possible. Only system level datasets > should be directly cataloged in the master catalog. > It also allows you to separate different applications into their own > usercatalogs for performance and security. > ... -- Joel C. Ewing, Fort Smith, AR [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
