Defining and Creating the RECON Data Sets

The RECON data sets are VSAM KSDSs. They must be created by using the VSAM AMS utilities. The RECON data sets:

• Must all use the same record size and CI size.

• Should be given different FREESPACE values so that CA and CI splits do not occur at the same time for both active RECON data sets.

• Should have different space allocation specifications to increase availability. The spare data set should be the largest RECON data set.

Figure 23-4 shows an example of a RECON data set definition.

Figure 23-4. Example of a RECON Data Set Definition

 DELETE STIMS220.RECONB  SET LASTCC=0  DEFINE CLUSTER (NAME(STIMS220.RECONB) -         VOLUMES (SBV0l0)                   -         INDEXED                        -         KEYS (24 0)                    -         CYLINDERS C5 2)                -         RECORDSIZE (128 32600)         -         SPANNED                        -         FREESPACE (30 80)              -         CISZ(4096)                     -         NOREUSE                        -         NERAS SPEED REPL IMBD          -         UNORDERED                      -         SHAREOPTIONS (3 3))            -  INDEX (NAME(STIMS220.RECONB.INDEX))    -  DATA (NAME(STIMS220.RECONB.DATA)) 

Placement Considerations for the RECON Data Sets

The placement of the RECON data sets in the DASD configuration is critical. The primary rule is to configure for availability. In doing so, you isolate possible failures. This means, for example, to place all three RECON data sets on:

• Different volumes

• Different control units

• Different channels

• Different channel directors