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Allocating New Disk Datasets
In an SMS (System Managed Storage) environment, some additional facilities
are available to simplify the JCL for allocating new datasets. For example,
the AVGREC parameter allows you to specify the size of a new dataset in
terms of the number of records. For example,
<![CDATA[
//NEW DD DISP=(,CATLG,DELETE),DSN=new.dataset.name,UNIT=SYSDA,
// AVGREC=U,SPACE=(80,(100,50),RLSE),RECFM=FB,LRECL=80
]]>
specifies that the primary size for the dataset is 100 records of size 80
bytes with a space increment of 50 records. For variable length records
(RECFM=VB), LRECL would be the maximum record length and the first subparameter
for the SPACE parameter would be the average record length.
You can also specify:
- AVGREC=K to specify the record count in K (1024 records)
- AVGREC=M to specify the record count in M (1024*1024=1,048,576 records)
Cloning an Existing Dataset
The LIKE parameter can be used to copy space and DCB attributes from an
existing dataset. For example,
<![CDATA[
//COPY EXEC SORT
//SORTIN DD DISP=SHR,DSN=input.dataset
//SORTOUT DD DISP=(,CATLG,DELETE),DSN=output.dataset,
// LIKE=input.dataset
//SYSIN DD *
SORT FIELDS=COPY
]]>
could be used to create a second copy of an existing dataset.
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