What is the difference between BLKSIZE and LRECL?

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What is the difference between BLKSIZE and LRECL?..

Answer / guest

LRECL is the length of ur record file.
Blksize is the length of the block in which records are
stored.It varies in case of fixed length records and
variable length records.
fixed length records-It is a multiple of lrecl.
e.g. suppose u have blksize =800 & lrecl=80.It means that
there are 10 records each of size 80.
variable length records-It is the length of longest record
in the block + 8 (bcoz. here lrecl=length of longest record
+4 & blksize=lrecl+4).

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What is the difference between BLKSIZE and LRECL?..

Answer / guest

LRECL is the logical record length , where as BLKSIZE is
multiples of LRECL

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What is the difference between BLKSIZE and LRECL?..

Answer / stu

Data is read and written to files in blocks. The reading
and writing of blocks is I/O. I/O is overhead (increases
runtime and cost) and you want to keep it to a minimum.

When reading a file, a whole block of records will be read,
but the records in the block will be fed to the program one
at a time until the block is exhausted and the next block is
read. The operating system does this behind the
scenes--it's transparent to the programmer.

When writing to a file, the records are not actually written
to the file until a block is full (or the program ends--at
which time the last block is written if it contains at least
1 record.) Again, this is transparent to the programmer.

Obviously, to keep I/O low, you want the cram as many
records into a block as possible.

Let's say your FB file's record length (LRECL) is 252 bytes
and your facility allows block sizes up to 27000 bytes.
Your blocksize would be ((integer (27000 / 250)) * 252) or
26964 (107 records).

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