CA Dynam for VSE User Guide

Basic Components
We recommend using Automatic Secondary Allocation, because it enhances
both performance and reliability. Performance is improved because with
Automatic Secondary Allocation active, CA Dynam/D generates only two
labels. Reliability is improved because all extents of a multi-extent input file
are found and read even if there are more of them than the number of EXTENT
statements in the JCL.
Examples
Following are three examples of defining files to the Catalog. For more
information, see the chapter "Maintaining the Catalog—DYNCAT Program."
Method One
Defining the file in the CA Dynam Catalog with a primary allocation only, and
allowing automatic secondary allocation to provide secondary extents. The
example assumes that the DYNAM/D option record has ASAAMT(30) (30%
primary allocation can be used for secondary allocation) and ASAMAX(3)
(maximum of 3 secondary allocations).
DISK.FILE is defined to the Catalog with 10 tracks for primary allocation, of
which 30% percent (3 tracks) is allowed for secondary allocation.
// JOB DEFINE ALLOCATION
// EXEC DYNCAT
DEFINE 'DISK.FILE' ALLOC=(SYSWK1,TRK,10)
/*
/&
// JOB USE FILE
// DLBL SDDOUT,'DISK.FILE'
// EXEC PROGRAM
CADD002I ALLOCATED FILE=SDDOUT SYS006=202 SYSWK1 X=0/7/10
CADD002I ALLOCATED FILE=SDDOUT SYS006=202 SYSWK1 X=1/17/3
CADD002I ALLOCATED FILE=SDDOUT SYS006=202 SYSWK1 X=2/20/3
CADD002I ALLOCATED FILE=SDDOUT SYS006=202 SYSWK1 X=3/23/3
Automatic Secondary Allocation (ASA) works in the same fashion from JCL
(that is, supply only one extent). Certain restrictions apply to using ASA for
files which are opened and closed multiple times in the same program. For
these files, if a generic volume serial number is used (for example, WORK**),
it is only effective for the first open which uses the label record.
Subsequent opens will use the resolved volume serial number where the file
was actually accessed or created (possibly WORK01). ASA is not supported for
SD TYPE=WORK files (compiler work files, FORTRAN disk files, and so on), or
ISAM or DA files.
Chapter 4: Disk File Management 4–5