VMS Help RMS, RMS Control Block Macros, $XABALL  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The $XABALL macro allocates and initializes a XABALL, which
    allows extended control of file disk space allocation, both for
    initial allocation and later extension. No value is returned for
    this assembly-time operation.

    Format

      $XABALL  AID=area-identification-number,

               ALN={ANY|CYL|LBN|RFI|VBN},

               ALQ=allocation-quantity,

               AOP=<CBT CTG HRD ONC>,

               BKZ=bucket-size,

               DEQ=extension-quantity,

               LOC=location-number,

               NXT=next-xab-address,

               RFI=<f(1), f(2), f(3)>,

               VOL=volume-number