Be sure the EXIT ADD EN(OCE_VOLUMEMOUNT) MOD(IFG019VM) statement is in a PROGxx member which is defined in IEASYSnn,
which is processed before the IBM default exit is installed. If that is not the case and the PROGxx member is activated using SET PROG=XX
later in the IPL process, this might be too late resulting in the error message above.
As per IBM documentation: "Controlling the volume mount exit routine through the dynamic exits facility" https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.idac700/oce_vm.htm
The system attempts to add exit routine OCE_VOLUMEMOUNT, unless an exit routine has been associated with OCE_VOLUMEMOUNT by PROGxx
or SETPROG. If you have associated exit routines with OCE_VOLUMEMOUNT the system does not use the default exit routine.
In this case, if you require an exit routine of the default name, you must explicitly add the default exit routine to PROGxx.
After Rel 14.0 PTF LU01354 the
PROGxx members of SYS1.PARMLIB must be:
EXIT ADD EXITNAME(OCE_VOLUMEMOUNT) MODNAME(CTS019VM)
in order for the CA1 utility TMSCKLVL and the TMS STATUS command to report on whether the FAILSAFE intercept is active or not.