Using compaction on SNA workstations

Compaction, which is available only for SNA NJE and RJE workstations, is used to increase data transmission efficiency by compacting master character pairs into a single 8-bit representation (4 bits per character).

Data transmissions to workstations and remote devices can be compacted if you specified compaction. The COMPACT initialization statement defines the characters to be compacted (master characters) and the characters to be recognized by the compaction routines but not compacted (nonmaster characters).

In the example below, the compaction table NEWONES specifies 15 master characters (the numbers 0-9 and the vowels A, E, I, O, and U) and 16 nonmaster characters. The NUMBER= parameter specifies a number by which both the installation and JES2 can refer to this table. If you do not specify a table name, NAME= defaults to the NUMBER= parameter value; therefore, you must specify the NUMBER= parameter.

COMPACT NAME=NEWONES,CHARS=(15,0,1,2,3,4,5,6,7,8,9,A,E,I,O,U,
        40,B,C,D,F,G,H,J,K,L,M,N,61,$,T,S),NUMBER=1

The COMPACT=YES parameter specification on the RMT(nnnn) statement, the $ADD RMT(nnnn) command, or the $T RMT(nnnn) operator command allows you to specify if an NJE or RJE workstation is to accept compacted data. The COMPACT parameter on the R(nnnnn).PR(m) and R(nnnnn).PU(m) statements is set equal to a valid compaction table identifier (which is specified on the COMPACT initialization statement) if compaction is required for the remote device. Also, the device must specify CMPCT=YES or JES2 does not compact the data.

The /*OUTPUT JES2 control statement or the JCL OUTPUT statement can be used to override the R(nnnnn).PR(m) and R(nnnnn).PU(m) statements. However, neither the /*OUTPUT statement nor the JCL OUTPUT statement has any effect on compaction for node-to-node transmissions (SNA NJE) because such compaction is done on a session basis. For further information, see z/OS MVS JCL Reference.