RMS_EXTEND_SIZE

   RMS_EXTEND_SIZE specifies the number of blocks by which files
   are extended as they are written. This number should be chosen to
   balance the amount of extra disk space wasted at the ends of each
   file against the performance improvement provided by making large
   extents infrequently.

   When small disk quotas are used, specify a small number such as
   the disk cluster size to prevent the user's disk quota from being
   consumed. If the value of 0 is used, RMS allocates large extents
   and truncates the file back to its actual usage when it closes.

   You can set this system parameter with the DCL command
   SET RMS_DEFAULT/SYSTEM and display the parameter with SHOW RMS_
   DEFAULT.

   RMS_EXTEND_SIZE is a DYNAMIC parameter.