General Guidance

You can identify user-written exit routines for use with non-VSAM access methods. These user-written exit routines can perform a variety of functions for non-VSAM data sets, including error analysis, requesting user totaling, performing I/O operations for data sets, and creating your own data set labels. These functions are not for use with VSAM data sets. Similar VSAM functions are described in Coding VSAM User-Written Exit Routines.

The DCB and DCBE macros can be used to identify the locations of exit routines:

The routine that performs end-of-data procedures (the EODAD parameter of DCB or DCBE).
The routine that supplements the operating system's error recovery routine (the SYNAD parameter of DCB or DCBE).
The list that contains addresses of special exit routines (the EXLST parameter of DCB).

The exit addresses can be specified in the DCB or DCBE macro, or you can complete the DCB or DCBE fields before they are needed. Table 1 summarizes the exits that you can specify either explicitly in the DCB or DCBE, or implicitly by specifying the address of an exit list in the DCB.

Table 1. DCB exit routines
Exit Routine	When Available	Topic
End-of-data-set	When no more sequential records or blocks are available	EODAD End-of-Data-Set Exit Routine
Error analysis	After an uncorrectable input/output error	SYNAD Synchronous Error Routine Exit
Allocation retrieval list	When issuing an RDJFCB macro instruction	DCB Exit List
Block count	After unequal block count comparison by end-of-volume routine	DCB Exit List
DCB abend	When an abend condition occurs in OPEN, CLOSE, or end-of-volume routine	DCB Exit List
DCB open	When opening a data set	DCB Exit List
End-of-volume	When changing volumes	DCB Exit List
FCB image	When opening a data set or issuing a SETPRT macro	DCB Exit List
JFCB	When opening a data set with TYPE=J and reading the JFCB	DCB Exit List
Standard user label (physical sequential or direct organization)	When opening, closing, or reaching the end of a data set, and when changing volumes	DCB Exit List
JFCB extension (JFCBE)	When opening a data set for the IBM 3800	DCB Exit List
Open/EOV nonspecific tape volume mount	When a scratch tape is requested during OPEN or EOV routines	DCB Exit List
Open/EOV volume security/verification	When a scratch tape is requested during OPEN or EOV routines	DCB Exit List
QSAM parallel processing	Opening a data set	DCB Exit List
User totaling (for BSAM and QSAM)	When creating or processing a data set with user labels	DCB Exit List