Cache Management › Dynamic Cache Management › Setting Up Dynamic Cache Management in SMS › SMS Data Class

SMS Data Class

CA Vtape requires that a data class with the following characteristics be defined:

Volume Count . . . . . . .: 16 
Data Set Name Type . . . .: EXTENDED 
  If Extended  . . . . . .: PREFERRED 
  Extended Addressability : NO 
  Record Access Bias . . .: USER 
Space Constraint Relief  .: YES 
  Reduce Space Up To (%) .: 50 
  Dynamic Volume Count . .: 59 

Note: A Record Organization (Recorg) of LS for Linear Data Set is not coded because this data class will be used for both VSAM and non-VSAM data set allocations. CA Vtape supplies the appropriate Recorg in its allocation requests.

The following explains each characteristic:

Volume Count

Reserves space in each cache LDS catalog entry for the number of volumes entered. 16 is recommended to reserve some space in the catalog entry for multiple volume allocations and to minimize the number of CI/CA splits versus the maximum of 59 which would eliminate all splits, but would require that a large catalog be defined.

Data Set Name Type

Extended ensures that the Virtual Volume Data Sets are allocated in extended format. This is required by partial space release, which is used to release unused DASD space allocated to a cache LDS.

Extended Addressability

Deals with data sets greater than 4 GB. If you intend to write Virtual Volumes of 8 GBs or 16 GBs, SMS requires that this be set to YES.

Record Access Bias

Allows CA Vtape to control record buffering.

Space Constraint Relief and Reduce Space Up To (%)

These parameters allow SMS to modify the space allocation requested by CA Vtape when the storage group becomes constrained for space.

Dynamic Volume Count

Allows the cache LDS to be spanned to this number of DASD volumes if they are available in the storage group.

The other data class characteristics can be left at their default value or blank.