CA Dynam for VSE User Guide

Changing File Characteristics
Storage Requirements
Carefully consider storage requirements when using CA Dynam/FI to increase
the block size or buffers of a file -- single buffering to double buffering (DB). If
additional storage is needed for the blocks or buffers, it is taken from partition
GETVIS. This storage can be considerable depending on the new block size
and/or buffer size.
Also be aware that it is not always an efficient use of storage to specify
BLKSZ=OPTIMIZE for a file that originally wrote small records in small blocks.
This is true, for example, if the device type is a 3380 disk drive.
Block Sizes and Logical Record Lengths
The logical record length (LRECL) and the physical block size (BLKSZ) can
affect each other, depending on the record format specified. CA Dynam/FI will,
if necessary, alter either or both the LRECL and BLKSZ, depending on both the
old and new record format. The exact conditions and actions taken are
described below.
Note that if the user specifies an LRECL or BLKSZ value through Job Control or
the Catalog, then CA Dynam/FI uses these values just as they are. However, if
either the LRECL or BLKSZ value is not specified through Job Control or the
Catalog, then one or more of the following can occur:
• If control characters for:
−
−
DTFPR (printer)files are added to records, then record length is
increased one byte.
DTFCD (punch) files are deleted from records, then record length is
decreased one byte.
• If changing from:
−
−
Fixed- or undefined- to variable-length records, then record length is
increased four bytes to include record descriptor word (RDW).
Variable- to fixed- or undefined-length records, then record length is
decreased four bytes and RDWs are eliminated.
• If record format is to be fixed-unblocked or undefined, then block size
equals record length.
• If record format is to be fixed blocked and:
−
Old format was fixed (blocked or unblocked), then block size equals
old blocking factor (old block size divided by old LRECL) multiplied by
record (current LRECL).
For example, if you specify RECFM=FB and LRECL=50 when:
old logical record length = 80
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