Control blocks

Figure 112 shows the control blocks associated with the trace domain.

Figure 112. Control blocks associated with the trace domain
 This figure shows the control blocks associated with the trace domain, as described in the text.
TR domain anchor block (TRA).
There is one TRA in the system. It contains all status information relating to the trace domain and also pointers to the other trace domain control blocks.
Internal trace table.
An area of virtual storage above the 16MB line used for recording trace entries.
TR block (TRBL).
The internal trace table consists of a number of TRBLs chained in a loop. They are each 4096 bytes long. Each block contains a standard header and a sequence of variable-length trace entries.
Trace entry (TREN).
All trace entries consist of a header together with any data specified on the call. The length of each trace entry is in the range 32 through 4072 bytes.
TR auxiliary trace data set DCB, DECB, and buffer.
During the auxiliary trace start process, an MVS™ GETMAIN is issued to acquire storage below the 16MB line for these areas. Their addresses are kept in the TRA. The storage is released when auxiliary trace is stopped.
GTF buffer.
During the GTF trace start process, an MVS GETMAIN is issued to acquire storage above the 16MB line for this area. It is 256 bytes long, and its address is kept in the TRA. The storage is released when GTF trace is stopped. The buffer is used when splitting large entries (more than 256 bytes) into 256-byte pieces to be written to GTF. This is done because GTF has a length restriction of 256 bytes.
Global trap/trace exit work area (TRGTW).
When the FE global trap/trace exit (DFHTRAP) is activated, an MVS GETMAIN is issued to acquire storage above the 16MB line for the TRGTW. This area contains a register save area and all working storage associated with DFHTRAP, including the parameter list passed to the exit program. Its address is kept in the TRA. The storage is released when the trap is deactivated.

See the CICS® Data Areas manual for a detailed description of these control blocks.

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