BLOCK0

BLOCK0 affects whether the default blocking specification for QSAM files is changed from unblocked to blocked.

Syntax

Read syntax diagramSkip visual syntax diagramBLOCK0=*NOYES
Default
BLOCK0=NO
YES
Changes the default blocking specification for QSAM files that specify neither BLOCK CONTAINS nor RECORDING MODE U in the file description entry. BLOCK0=YES activates the BLOCK CONTAINS 0 clause for such files, causing them to have a system-determined block size at run time.

Performance consideration: Using BLOCK0=YES could result in enhanced processing speed and minimized storage requirements for QSAM output files. But see the recommendation below.

NO
Does not activate the BLOCK CONTAINS 0 clause by default for any file.

Recommendation: Adding a BLOCK CONTAINS 0 clause to file descriptions in existing programs could result in a change of behavior in those programs, including some undesirable effects for files opened as INPUT. For this reason, it is recommended that BLOCK0=YES not be set as an installation default.

For further details, see BLOCK0 in the Enterprise COBOL Programming Guide.