Recently Introduced z/OS Features that may be of interest to installations running Allocate DASD Space and Placement

Products

• Allocate DASD Space and Placement

Issue/Introduction

Below are the recently Introduced z/OS Features that may be of interest to installations running Allocate DASD Space and Placement.

Resolution

• Dynamic Volume Count Parameter Added to Minimize Out of Space Situations
  DYNVOL is a DFSMS Dataclass attribute acting the same way as either specifying a unit count in the JCL, as in UNIT=(SYSALLDA,4), or candidate volumes (*) in an IDCAMS DEFINE, as in VOLUMES(SMD007 * *). DYNVOL will add candidate volumes to data sets "up front", when the data set is created. Then later, should the data set need to span onto an additional volume DFSMS will automatically select it from the appropriate DFSMS Storage Group. In addition to the features described above, Allocate EOV Environment allows changes to be made to the space allocation amounts at the time a data set encounters an EOV condition for both Non-SMS and SMS-Managed data sets.

 

• SMS Overflow Storage Group (OSG)
  This new feature is limited to new SMS-Managed data set allocations. It's very similar to Allocate long outstanding ability to redirect NonSMS-Managed data sets, both when new and when old at EOV-time, to multiple storage groups (SGs).

  Introduction of this new feature in no way prevents you from continuing centralizing SMS and non-SMS data set allocation management in Allocate without the need to implement DFSMS ACS routines. Existing code can "SET" multiple SMS SGs in the ACS Environment the same way it can set multiple NonSMS-ones in the ALLOC, DEFINE, EOV, and EOV_VSAM Environments.

• SMS Extend Storage Group (ESG)
  Unlike the new OSG feature, which is just a yes/no indicator that may refer to more than one SG, the new EXTEND SG NAME STORCLAS attribute actually contains the name of the single additional SG DFSMS will allow a data set to span onto. The ESG will be used only for a SMS-Managed data set to extend onto when there isn't another volume available for it in the SG the data set was originally allocated in.

  DFSMS will select a volume from the ESG only when the data set already has candidate volumes in excess of available volumes in SMS SG it was originally allocated in. There are three ways to insure a data set has available candidate volumes. Either via he new DYNVOL parameter, the old unit-count JCL parameter, or Allocates existing End-Of-Volume Support for SMS-Managed data sets.