Restrictions

If the last block is truncated, you should never extend a standard-format data set by coding:

EXTEND or OUTINX on the OPEN macro
OUTPUT, OUTIN, or INOUT on the OPEN macro with DISP=MOD on the allocation
CLOSE LEAVE, TYPE=T, followed by a WRITE
POINT to after the last block, followed by a WRITE
CNTRL on tape to after the last block, followed by a WRITE

If the data set becomes extended, it contains a truncated block that is not the last block. Reading an extended data set with this condition results in a premature end-of-data condition when the truncated block is read, giving the appearance that the blocks following this truncated block do not exist.

Standard-format data sets that end in a short block on magnetic tape should not be read backward because the data set would begin with a truncated block.

A format-F data set will not meet the requirements of a standard-format data set if you do the following:

Extend a fixed-length, blocked standard data set when the last block was truncated.
Use the POINT macro to prevent BSAM from filling a track other than the last one. Do not skip a track when writing to a data set.

Standard format should not be used to read records from a data set that was created using a record format other than standard, because other record formats might not create the precise format required by standard.

If the characteristics of your data set are altered from the specifications described above at any time, the data set should no longer be processed with the standard format specification.