Origin of GSAM data set characteristics

For an input data set, the record format (RECFM), logical record length (LRECL), and block size (BLKSIZE) are based on the input data set label.

If this information is not provided by a data set label, the DD statement or the DBD specifications are used. The DD statement has priority.

An output data set can have the following characteristics:

Specify the record format on the DATASET statement of the GSAM DBD. The options are:

The V, F, or U definition applies and is not overridden by the DCB=RECFM= specification on the DD statement. However, if the DD RECFM indicates blocked and the DBD does not, RECFM is set to blocked. If the DD RECFM of A or M control character is specified, it applies as well.

Unless an undefined record format is used, specify the logical record using the RECORD= parameter of the DATASET statement of DBDGEN, or use DCB=LRECL=xxx on the DD statement. If the logical record is specified on both, the DD statement has priority. Refer to the following table for the maximum record length

Table 1. BSAM and VSAM logical record lengths for GSAM data sets by record format
Record Format BSAM logical record length VSAM logical record length
Fixed/Fixed Block 32760 bytes 32760 bytes
Variable/Variable Blocked 32756 bytes 32756 bytes
Undefined 32760 bytes not supported

Specify block size using the BLOCK= or SIZE= parameter of the DATASET statement of DBDGEN, or use DCB=BLKSIZE=xxx on the DD statement. If block size is specified on both, the DD statement has priority. If the block size is not specified by the DBD or the DD statement, the system determines the size based on the device type, unless the undefined record format is used.

The other JCL DCB parameters that can be used, include:

Restriction: Do not use BFALN, BUFL, BUFOFF, FUNC, NCP, and KEYLEN.