IBM OS/390 User Manual

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For unlabeled tapes - the DEVADDR is the only link between the program
and the JCL (there is no TLBL). Either the DEVADDR or the DTFname can be
used as DDNAME.
For card devices - the DEVADDR links the DTF to a card reader or puncher;
Either the DEVADDR or the DTFname can be used as DDNAME.
For print devices - the DEVADDR is the only link to a printer or a LST card.
Either the DEVADDR or the DTFname can be used as DDNAME.
4.3.7 Catalogs
With the exception of VSAM, in VSE JCL there are no catalogs to deal with. The
user must provide an extent for each read or write to a disk file.
For tape functions the correct tape must be mounted. Volume information must
be specified for disk files using an EXTENT card, except for files managed by
VSAM, which are managed in a VSAM catalog.
There are vendor products in the marketplace that provide these cataloging
functions, such as Dynam and EPIC. Many VSE installations use one of these
products for disk management, tape management, or both. Installations that do
not use a third-party disk manager often make extensive use of VSAM-managed
SAM files.
4.3.8 Partition Dependent Codes in JCL
4.3.8.1 Procedures
Partition-dependent codes in VSE JCL can ensure that a procedure runs in a
particular partition. Procedures may be cataloged names in the form of $xABC
(where x = 1, 2, 3,... B = representing BG, F1, F2, F3,... FB partitions). A job
may be built with an EXEC PROC=$$ABC and run in various partitions. When
run in BG, $0ABC.PROC will run; when run in F5, $5ABC.PROC will run; and so
on. MVS, which has no notion of 
partition
″, 
has no equivalent function.
4.3.8.2 Data Set Names
Data set names can contain the condition dependent operands; 
′ % % ′ .
The first
′%′ 
is partition, the second 
′%′ 
is the view.
This function is similar to the DSN=&&dsname function in MVS, which allows
use of the same JCL in concurrently running jobs without having conflicts with
the data set names.
4.3.9 Communication Region - DATE and UPSI
4.3.9.1 DATE
In VSE, the date is stored in the Job Date field of the partition
s communication
region. There is only one facility in VSE from which to get the date. The date can
be entered in the JCL and is what the job will see whenever the application
queries the system date. The result will be the date that is specified in JCL.
The VSE DATE function allows a job to run with a date that is not the system
date. It can also ensure that when a job that takes an hour to run is started at
23:30, the steps that execute after midnight will maintain the same date.
Chapter 4. Job Control Language (JCL) Differences and Considerations
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