Transactional execution diagnostics

A program interrupt within a transaction is identified by bit 6 of the 16-bit interrupt code's being on. Thus, for example, a protection exception within transactional execution mode would be interrupt code X'0204'.

If the transaction gets a program interrupt that is not filtered (TBEGIN can identify some filtering of program interrupts), normal z/OS program interrupt processing occurs (and the transaction is aborted). Information about the PSW and registers at the time of the program interrupt are captured by the system and made available to your recovery routines, and certain diagnostic "rules" are applied.

ESPIE exit routines will get both the time of error registers/PSW and the transaction-begin registers/PSW.

Bit EPIEPITX: The program interrupt occurred while within transactional execution.
Existing fields EPIEGPR, EPIEG64S contain the time of error register information. When bit EPIEPITX is off, these are the registers current when the program interrupt occurred. When bit EPIEPITX is on, these are the registers that resulted from the transaction abort due to the program interrupt. Resume is done using these fields whether or not bit EPIEPITX is on.
Existing fields EPIEPSW, EPIEPSW16 contain the time of error PSW information. When bit EPIEPITX is off, this is the PSW current when the program interrupt occurred. When bit EPIEPITX is on, this is the PSW that resulted from the transaction abort due to the program interrupt (for a nonconstrained transaction, the address will be of the instruction following the TBEGIN; for a constrained transaction, the address will be of the TBEGINC instruction). Resume is done using these fields whether or not bit EPIEPITX is on.
When bit EPIEPITX is on, new field EPIETXG64 contains the registers current when the program interrupt occurred.
When bit EPIEPITX is on, new field EPIETXPSW16 contains the PSW current when the program interrupt occurred.

Note: A SPIE exit routine will not get control for a program interrupt during transactional execution.

For a recovery routine (whether FRR-type or ESTAE-type), there will be additional information in the SDWA:

Bits SDWAPTX1 (within byte SDWAIC1H in field SDWAAEC1) and SDWAPTX2 (within byte SDWAIC2H in field SDWAAEC2): The program interrupt occurred while within transactional execution and therefore bit SDWAPTX1 is valid only when bit SDWAPCHK is on.
Existing fields SDWAG64, SDWAG64H, and SDWAGRSV contain the time of error register information. These are the registers current when the program interrupt occurred.
Existing field SDWAPSW16 contains the time of error register information. This is the PSW current when the program interrupt occurred.
When bits SDWAPCHK and SDWAPTX2 are on, new field SDWATXG64 contains the registers that resulted from the transaction abort due to the program interrupt.
When bits SDWAPCHK and SDWAPTX2 are on, new field SDWATXPSW16 contains the PSW that resulted from the transaction abort due to the program interrupt.

The IEATXDC service is provided to help you test your applications. A nonconstrained transaction has both a transactional path and a fallback (non-transactional) path. With the IEATXDC service, you can request random aborts of transactions for your work unit so that, upon repeated runnings, you are likely to exercise both the non-abort and abort paths.

Debugging of problems that might occur within transactional execution mode can be much more difficult than others since any stores done within the transaction have been rolled back by the time that the system gets to examine the time of error data. SLIP provides some help in this area:

A new ERRTYP option, TXPROG, is supported. When specified, the SLIP trap will match only if the event was a program interrupt error event that occurred within transactional execution mode.
The SLIP DISPLAY of an active trap will display, when non-0, the number of times that the SLIP trap was examined, but did not match because of the DATA keyword (in a transactional execution case, this could be normal, because the stores were rolled back when the error or PER program interrupt occurred). This is referred to as the transactional execution DATA filter mismatch count.
Note: If the value is 255, the count of events could have exceeded 255.
SLIP provides a new keyword TXIGD, Transactional eXecution IGnore Data, which indicates that a SLIP trap is to ignore the DATA keyword filter that is also present in this trap if the event (whether error or PER) occurred while within transactional execution. This keyword may be specified on SLIP SET, and also may be used on SLIP MOD. You might use TXIGD in the following case:
- Your SLIP trap with a DATA filter did not match, but the event still occurred.
- The display of the SLIP trap showed a non-0 transactional execution count.
- You think that roll back of stores when the transaction aborted might have led to the DATA filter's not matching.
- By ignoring the DATA keyword, the trap might match and even though it will not have a DATA filter applied as a result, it might match the right event.
The NOTXIGD keyword may also be specified.

The SLIP GTF record, at offset (decimal) 135, has a 1-byte count that is the transactional execution DATA filter mismatch count.