Using VSAM ESDS files with QUICKSTART

Just as standard sequential files can be accessed by making CALLs to QUICKSAM, so can VSAM ESDS datasets. VSAM ESDS datasets are very similar in nature to files accessed with the QSAM or BSAM access methods in that an ESDS is processed sequentially from beginning to end. When using VSAM ESDS datasets, there are a few simple rules to follow to ensure restartability.

VSAM datasets are created using the utility IDCAMS. Hence, they are always predefined. This allows the JCL on the job step to always state DISP=OLD or DISP=SHR for both input and output functions.

When using QUICKSAM to write to an ESDS dataset, the dataset must be created using the RECOVERY keyword on the IDCAMS DEFINE statement. This is not necessary for input datasets. For output datasets, the REUSE keyword is also recommended to prevent having to DELETE/DEFINE the VSAM Cluster before each initial run. A sample IDCAMS DEFINE for an output ESDS dataset follows:

VSAM ESDS records may be fixed length, variable length, or variable length spanned. The RECSZ and SPANNED parameters of the IDCAMS DEFINE control these attributes. The use of variable length records with QUICKSAM is identical to that of standard variable length files and the procedure in Choosing-the-appropriate-processing-mode should be followed.

If any errors are encountered when READing or WRITEing VSAM ESDS datasets, QUICKSAM will ABEND. At ABEND time, Register 10 will point to a VSAM Debugging Area which is 8 words (32 bytes) long. The first 4 words (16 bytes) contains the eye-catcher 'VSAM DEBUG AREA'. The next 4 words (16 bytes) contain the contents of REGISTER 0, REGISTER 15, the address of the VSAM ACB, and the address of the VSAM RPL, in that order. Depending on the error encountered, some of this data may not be applicable.