VM66724: INCREASE CMS TAPE BLOCK SIZE

Obtain the fix for this APAR.

APAR status

• Closed as new function.

Error description

• Increase the block size supported for native CMS tape I/O from
  64KB to approximately 1MB.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of products or applicatons that        *
  *                 exploit native CMS tape I/O functions        *
  *                 (RDTAPE and WRTAPE)                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  ****************************************************************
  * RECOMMENDATION: APPLY PTF                                    *
  ****************************************************************
  The native CMS tape support block size limit is increased from
  64K to roughly 1M. This enables applications and products such
  as backup solutions that exploit the native interfaces to use
  larger blocks, which can improve their performance.
  

Problem conclusion

Temporary fix

• FOR RELEASE ES-CMS-730-BASE :
  PREREQ: NONE
  CO-REQ: NONE
  IF-REQ: NONE
  

Comments

• Tape channel programs are now constructed using multiple
  data-chained CCWs to accommodate a larger block size.
  The maximum tape blocksize supported is available in a new field
  in NUCON, MAXTAPBS. In CMS releases without this support, this
  field is zero, indicating that the maximum block size is 65,535.
  The RDTAPE macro no longer limits a numeric buffer length to
  65,535 bytes. The associated MNOTE is no longer produced and the
  buffer length is not changed. The length is still checked at run
  time and will produce return code 1 if it exceeds the supported
  maximum.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  UM90377

Modules/Macros

• DMSNUC   DMSTIO   DMSTLB   DMSTLW   DMSZNUC  NUCON    NUCONP
  NUCONPZ  NUCONZ   RDTAPE   WRTAPE
  

Fix information

• Fixed component name

  VM CMS

• Fixed component ID

  568411201

Applicable component levels

• R730 PSY UM90377

     UP23/11/14 P 2401  

Fix is available

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