Required parameters

session_id

Specifies the name of an XRC session. This can be any name acceptable to TSO except for the word ALL, which is reserved. The maximum length of the name is eight characters. Do not include embedded blanks. TSO ignores leading blanks and trailing blanks.

ERRORLEVEL

Specifies how the XRC session responds when an error occurs that causes the session to become unable to process a volume. You can abbreviate this parameter as ERRLVL.

The error level you specify with the XSTART command is the default for all volumes that do not have an error level specified with an XADDPAIR command. The error level specified with the XADDPAIR command overrides the error level specified with the XSTART command. For example, if you specify ERRORLEVEL(SESSION) for a volume pair on an XADDPAIR command, an error on that duplex volume pair results in the suspension of all volumes in the XRC session, even if ERRORLEVEL(VOLUME) was specified on the XSTART command.

XRC supports multiple levels of error processing within a single session. Critical volumes can have ERRORLEVEL(SESSION), while all other volumes can use ERRORLEVEL(VOLUME) or ERRORLEVEL(group_name).

The values are:

SESSION: Specifies that, if a permanent error to a duplex primary or secondary volume occurs, XRC suspends all volume pairs in the XRC session, regardless of the volume status. Suspending any volume pairs from the session can negatively affect the usability of the remaining secondary volumes. Specify SESSION to ensure that all secondary volumes in the entire XRC session that are necessary for recovery are consistent up to the time of failure.
For sessions that will be coupled, use ERRORLEVEL(SESSION) to ensure a recoverable consistency across all coupled sessions.
VOLUME: Specifies that, if a permanent error occurs on a duplex volume, the XRC session suspends the volume pair or pairs that are associated with the error. All other volumes continue to process.
group_name: Specifies that, if an error to a duplex primary or secondary volume pair occurs, XRC suspends all volume pairs that are associated with that group name.
The group_name can be any name acceptable to TSO. The maximum length of the name is eight characters. Do not include embedded blanks. TSO ignores leading blanks and trailing blanks. Do not use the reserved names VOLUME and SESSION.

Note: For coupled sessions, error processing for volumes that are contained in a group will only pertain to the volumes within that session.

SESSIONTYPE

Specifies the operating mode (MIGRATE or XRC) for the XRC session. To change the mode of operation, suspend the session with an XSUSPEND command, followed by an XSTART command with a new SESSIONTYPE parameter. The values are:

MIGRATE: Specifies that the system data mover apply updates to the secondary volumes on a consistency group basis, but not write updates to the journal data sets. You must already have allocated the XRC state data set. The journal and control data sets are not used.
XRC commands maintain data consistency within a migration session in the same way as in a recovery session. If a disaster occurs while in SESSIONTYPE(MIGRATE) mode, XRC cannot guarantee data consistency across the secondary volumes, as there is no journaling activity. You can issue an XRECOVER command after ending a session in MIGRATE mode to clip the secondary volume serial numbers.
XRC: Specifies that XRC operate in recovery mode. A SESSIONTYPE(XRC) session makes use of journal volumes to guarantee secondary volume consistency group time. If XRC removes a volume from the session due to an I/O error, XRC can no longer update the secondary volume. Subsequent updates to the primary volume are lost if you must recover the applications on the recovery system.