IBM SC33-1683-02 - Manual (Page 73)

Exit XXDTO
When invoked
By an alternate CICS when it performs takeover under the following
conditions:
v The active and alternate CICS systems are in different MVS images,
perhaps in different processors.
v The active CICS was connected to, or trying to connect to, a DBCTL
subsystem. (This does not include disconnecting from one DBCTL and
reconnecting to another.)
v The takeover was not initiated by the XXDFB exit, or the takeover was
initiated by XXDFB but the active system reestablished a DBCTL
connection before takeover occurred and XXDTO was driven for a new
DBCTL takeover decision.
Exit-specific parameters
UEPDBXR
Address of CICS XRF information for use with DBCTL. The CICS
XRF information can be mapped using the DSECT DFHDXUEP.
Return codes
UERCNOAC
Take no action.
UERCSWCH
Switch to the alternate DBCTL.
UERCABNO
Abend CICS without a dump.
UERCABDU
Abend CICS with a dump.
The return code UERCNORM is not available for use at this exit point.
XPI calls
The following must not be used:
INQUIRE_MONITORING_DATA
MONITOR
TRANSACTION_DUMP
WRITE_JOURNAL_DATA.
DBCTL tracking program exits
Chapter 1. Global user exit programs 41