Design Example

The following is a high-level example of a CTRACE buffer find exit routine:

Locate the work area (field CTXIUSWA in the CTXI data area) and determine if this routine has been called before.
For the first call to this routine, do the following:
1. Initialize CTXIUSWA.
2. Use IPCS exit services or CTXI USERDATA, or both, to locate control information in the dump needed to identify the trace buffers. Save the anchor address in the work area.
Locate the next trace buffer defined by the CTRACE control structure. Save the buffer identified in the work area.
Fill in the ES record to identify the trace buffer.
The first time the exit is called, BLSRESSY is in 31-bit format. The storage is large enough to hold the 64-bit format. When working with 64-bit data, the buffer find exit converts BLSRESSY to the 64-bit format by invoking BLSRES02.

BLSRES02 is an IPCS service that receives the symbol table record (31 or 64 bits) and formats it into a 64-bit output symbol table record. From then on the 64-bit format of BLSRESSY is used every time the exit is invoked.

BLSRES02 is invoked using CALL with standard register conventions. For example:
CALL BLSRES02(ZZ2,ESPA,ESP2)
where:
INPUT= ZZ2 - IPCS task variable
ESPA - EQUATE Symbol Record Parameter
OUTPUT= ESP2 - 64 Bit Symbol Table Parameter
Set the return code.
Return to the caller.