Restrictions During the Runtime of the Bridge Subsystem

During the runtime of the bridge subsystem, some restrictions must be considered.

Read-only Mode for Some Tables

During the bridge phase, ZDO sets some tables to read-only mode for the following different reasons:

a complex structural change
a conflicting table access by XPRA, XCLA, or After Import Method in phase XPRAS_AIMMRG
a technical restriction because of the ZDO procedure

Normally, a read-only table does not affect the productive use of the system. The Impact analysis can detect possible read-only conflicts already during text cycles in the sandbox system. For more information, see Impact Analysis Usage.

Maintenance Mode in SUM

The update procedure with ZDO runs according to the maintenance mode of SUM. This means that the following update-related restrictions of the maintenance are active during ZDO process:

Workbench lock	As in the standard update procedure, the system is locked against the creation, modification, and deletion of Workbench objects after the LOCK_EU phase has been reached.
Transport lock	As in the standard update procedure, the system is locked against the import of transport requests after reaching the phase LOCK_EU.
Customizing lock	The system is locked against customizing changes. Exceptions to this are changes made during the runtime of the bridge subsystem as Current settings. Note In productive environments, it is not a restriction, because the customizing is not changed directly in the productive system. Customizing that has been modified in the bridge subsystem to match the Current settings can cause unexpected dumps because the corresponding tables are set to read-only during by the ZDO procedure.
Transaction RZ10	The transaction RZ10 is disabled during operations on the bridge subsystem. For more information, see SAP Note 2007911 .
Number ranges	Changes to number range intervals are not allowed during operations on the bridge subsystem. This can lead to inconsistencies in number assignment.

Native Database Connections to the Original Database Schema

As described in Technical Details of the Zero Downtime Option, the database schema changes during the rollover to the bridge subsystem.

If an external application or system uses native database connections to the original database schema (such as SAPHANADB), the application will be connected to the data belonging to the target release during the runtime of the bridge subsystem. Therefore, all native database connections must be disconnected as soon as the rollover to bridge is carried out in phase REQ_USER_ROLLOVER_PREP.

The connection can be re-established after the restart as soon as the phase REQ_USER_ROLLBACK_FINAL is reached.