Exit E18 is only used for sorts and exit E38 only for merges or copies. Each exit is entered exactly once, at the start of SORTIN processing. At this time, MFX checks Register 1 for the address of a user parameter list specifying the various open and error exit routines that you want MFX to include. MFX will then enter these routines at the appropriate times during execution. Because use of these exits forces the use of BSAM for the input file(s), performance may be adversely affected.
The format of the parameter list is given below. More information on the DCB fields can be found in the appropriate IBM publication.
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SYNAD field |
Indicated by 01 in byte 1. The SYNAD field contains the address of a synchronous read error routine, assembled as part of the exit program. Note that you may not use Register 13 as a save area pointer on entry to your routine. You must either provide your own save area or use the SYNADAF macro instruction. |
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EXLST field |
Indicated by 02 in byte 1. The EXLST field contains the address of a list of pointers to user routines that perform operations such as label checking. Note that in the event that the list contains a DCB-exit entry, it will not be entered during concatenated SORTIN processing. |
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EROPT code |
Indicated by 03 in byte 1. Bytes 2 and 3 contain zeros, byte 4
the EROPT code. This code tells MFX what action to take if it
discovers an uncorrectable read error on a non-VSAM input
file.
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EODAD field |
Indicated by 04 in byte 1. The EODAD field contains the address of an end-of-file routine. It can only be used with an E18 exit. |