When using application programs in a multiple-domain environment, consider taking advantage of the data compression facility. This facility enables VTAM® to compress the data for messages on selected LU-LU sessions. Data compression is transparent to application programs.

When using application programs in a single-domain environment, between application-to-application sessions in the same host, there is no benefit to compressing data. In fact, extra processing cycles are expended. If the SLU is an application in the same host, VTAM builds the BIND without data compression even if data compression is indicated. Data compression is not allowed in these single-domain conditions.

Also, you should not use the data compression facility for VTAM in conjunction with any application program data compression. After the application program has compressed the data, the amount of additional compression would be minimal.

You can implement data compression for logical units in either an extended BIND (types 2.1, 4, or 5 physical unit) or nonextended BIND environment (type 1 or type 2 physical unit). You cannot compress data for sessions with LU type 4 or LU type 7 in a nonextended BIND environment.

Data compression uses data storage.