Checking important fields in the SDWA
- Why the routine was entered.
The routine can check the SDWACMPC field, which contains the completion code that existed when the system gave control to the routine, and the SDWACRC field, which contains the reason code associated with the completion code. SDWACRC contains a reason code only if the SDWARCF bit is on.
- The location of the parameter area that was passed
by the mainline.
The routine can check the SDWAPARM field, which provides the information the routine needs to locate the parameter area. The contents of this field vary depending on the way in which the recovery was defined.
- Whether this is the first recovery routine to
get control.
If the SDWAPERC bit is off, this recovery routine is the first to get control. If the SDWAPERC bit is on, percolation has occurred.
The first recovery routine to get control usually has a more direct relationship with the error; being the first recovery routine to get control for an error can be an indication that the error occurred in the mainline routine that activated this particular recovery routine, rather than in a routine that was subsequently called.
This information can be useful in determining what action the recovery routine should take. A recovery routine is more likely to take corrective action or capture serviceability data if it is the first to get control for an error. Subsequent recovery routines are further removed from the error, and might limit their activities to releasing resources, or attempting a retry if possible.
The SDWAPERC bit is significant only between similar types of recovery routines. An ESTAE-type recovery routine can tell only if another ESTAE-type recovery routine has percolated; an FRR can tell only if another FRR has percolated.
See Important fields in the SDWA for a list of some of the fields in the SDWA, and an explanation of their contents.