Example: switching system modes

The following scenario uses XRC to support migration of a data center from one site to another site. After the migration, the scenario shows how the XRC session mode can be changed to activate the SDM in a disaster recovery mode.

Start a session named TUCSON for data migration with the state data set under a high-level qualifier of NEW.
```
XSTART TUCSON SESSIONTYPE(MIGRATE) ERRORLEVEL(VOLUME) HLQ(NEW)
```
Note: An error on any volume suspends the volume; other volumes continue to be copied.
Add a volume pair to the session for migration.
```
XADDPAIR TUCSON VOLUME(PRIM01,SECO01)
```
The error response level defaults to what is specified on the XSTART command.
Add another volume pair to the XRC session, specifying the error response level as VOLUME.
```
XADDPAIR TUCSON VOLUME(PRIM02,SECO02) ERRORLEVEL(VOLUME)
```
Normal data processing continues.
Quiesce the application programs prior to issuing the following XSUSPEND command.
```
XSUSPEND TUCSON DRAIN TIMEOUT(03.30.00)
```
In this example, the DRAIN keyword ensures that all updates in the storage controls are applied to the secondary volumes. The timeout duration of three hours and 30 minutes means that you plan to restart this XRC session with an XSTART command before this timeout duration has passed.

During the suspension, storage controls that support hardware bitmapping record application updates in their hardware bitmaps. Storage controls that do not support hardware bitmapping do not record application updates. Instead, updates accumulate in cache until the XSTART command function is complete.
Restart the application programs and the session. Restart the session as a disaster recovery session. The XSTART command must complete before the storage control timeout expires, or else the XRC session is ended.
```
XSTART TUCSON SESSIONTYPE(XRC) ERRORLEVEL(VOLUME) HLQ(NEW)
```
An error on any volume causes that volume to be suspended; other volumes continue to be copied. The state, control, and journal data sets are under a high-level qualifier of NEW.
Resynchronize the volume pair in the session.
```
XADDPAIR TUCSON VOLUME(PRIM01,SECO01)
```
The error response level remains what was initially specified prior to the suspension.
Resynchronize the volume pair in the session.
```
XADDPAIR TUCSON VOLUME(PRIM02,SECO02) ERRORLEVEL(SESSION)
```
The error response level for this volume pair is changed to SESSION. (Normal data processing continues.)
Issue the following command when a disaster occurs. This command is issued at the recovery site to apply in-progress updates to the secondary volumes and clip the secondary volumes to the primary volume serial numbers.
```
XRECOVER TUCSON HLQ(NEW)
```
The recovery is complete with the secondary volumes consistent up to the time reported by the XRECOVER command.