This section shows the backup and recovery strategies during a maintenance event with Zero Downtime Option (ZDO) of Software Update Manager.
When you are performing a ZDO upgrade, database logging as well as the HADR solution (only if available in the system) run throughout the complete upgrade, which includes the uptime on the bridge subsystem. Additionally, regular backups of the file system and database are regularly triggered in the background. While the complete upgrade is performed in parallel to productive business operations of end-users, it is ensured by Software Update Manager that the upgrade could be revoked at any time in case of an issue related to the upgrade procedure.
The revoke of the upgrade will be executed by the built-in reset feature in Software Update Manager. However, if the upgrade already passed the restart and switch to the target release, the reset is no longer possible. For this scenario, it is recommended to take a backup to recover the system to a consistent state before the restart happened.
Resetting the ZDO Procedure
Software Update Manager is equipped with a built-in reset feature that removes all upgrade-related artifacts in the system as well as in the database.
Like in every Software Update Manager upgrade, the reset can be started in the Software Update Manager user interface by choosing Reset in the menu. In Zero Downtime Option, the reset procedure is different in case the rollover to the bridge subsystem already happened. Hence, there are two cases that should be considered:
Case A: Reset before rollover to bridge
As long as the business users were not rolled over to the bridge subsystem and the phase REQ_USER_ROLLOVER_PREP has not been passed, the reset is executed like in the standard upgrade procedure during uptime processing. For more information, see the Software Update Manager Guide chapter Running the Software Update Manager → Working with the Software Update Manager Tool → Resetting the Update.
The complete reset happens in uptime and end-users are not impacted.
Case B: Reset during bridge runtime
Caution
Make sure that the phaseREQ_USER_ROLLBACK_PREP has not been passed. If this occurs, the switch to the target release would have happened already. In this case, a restore of the system is required in order to use the reset option in Software Update Manager. For details on backup and restore in ZDO, see the section Backup Request in Software Update Manager of this lesson below.Start the reset procedure in the same way as described above. In the Software Update Manager UI, choose Menu → Reset.
If the user rollover to the bridge subsystem has already been performed and the phase REQ_USER_ROLLOVER_PREP is completed, the reset is split into two steps:
Step 1 will remove the read-only restrictions on the tables. After this removal, the users can continue with regular production operation and all read-only tables are writable again. The target versions of tables (cloned tables) are no longer written. This step happens in uptime and end-users are not impacted.
Step 2 removes all artifacts related to the bridge subsystem. The reset procedure for ZDO is executed completely in the uptime.
Caution
Step 2 of the reset procedure requires a downtime if the SAP Kernel version is lower than 781. You can push this downtime to the next regular downtime window according to your maintenance plan.Backup Request in Software Update Manager
During a ZDO update, the business users continue to work until the very end of the maintenance event. Only for the time of the cut-over, the users have to log off from the system. Assuming a major issue would happen after switching over to the new release, the system has to be restored to a point in time where the source release was active. For this, a consistent full system backup is recommended that includes:
- a synchronous state of the database
- the Software Update Manager directory
- the system and instance directories
- the kernel directory
A dialog asks you in the phase SUMASK_ZDO_CONFIGURATION whether you want to run a system backup during the transition from the bridge subsystem to the target subsystem.
If the checkbox Yes, request the backup in the Configuration phase SUMASK_ZDO_CONFIGURATION (1) is checked, a further dialog in phase REQ_ZDO_SYSTEM_BACKUP (2) of roadmap step Postprocessing prompts you to start the system backup.
The dialog phase REQ_ZDO_SYSTEM_BACKUP is executed only after you initiated the rollback to the original system in the target release in the phase REQ_USER_ROLLBACK_PREP. The phase prompts you to start the system backup:
123The Bridge subsystem has been stopped.
Caution: To be able to reset the ZDO upgrade from this point, back up now the complete Software Update Manager directory including all subdirectories! Also, the current state of the database, the system and instance directories, and the kernel directory need to be taken to be able to restore to a consistent state.
Hint
If the system backup is taken in the phaseREQ_ZDO_SYSTEM_BACKUP, also the reset functionality is available until the same phase (REQ_ZDO_SYSTEM_BACKUP). In case of a major issue, the restore would bring back the system to this phase. From here, you can perform the reset as described above in case B.