Downtime minimization when upgrading BW systems

This blog has the focus on updates of SAP BW and considers downtime minimization capabilities of SUM and the benefits for the SAP BW.

The BW upgrades are related to

• SAP BW Updates and Upgrades,
• DB upgrades,
• custom development updates and releases.

For SAP updates you can use SPAM or the Software Update Manager (SUM)

The tool for upgrading SAP systems or updating bigger SP stacks is the Software Update Manager (SUM). This tool offers different mode to balance out the parameter of update run time, downtime and hardware.

SUM offers the following modes in general:

• „Single System“

No use of downtime optimization in SUM. This means no parallel execution of a shadow instance, including of customer transports buffer is not supported. The single system mode for updates needs the longest duration of downtime. But the overall SUM runtime is the shortest comparing with the other modes of SUM.

• „Standard“

A shadow instance is used to optimize the downtime because the DDIC update is therefore executed in uptime (pre-processing phase of SUM). No intensive use of hardware, the number of processes is more conservative. In standard mode the customer transport buffer can be included in general.

• „Advanced“

The hardware is used intensively to minimize the downtime of the SUM procedure. The extended shadow instance can be used for the nZDM feature of SUM. The customer transports buffer is included as well and also table conversion of customer tables can use the extended buffer as well. The number of processes can are extended and can be maintained

An additional “mode” will be the zero downtime option of SUM (ZDO). It uses the shadow operation for DDIC similar to standard mode but uses an additional instance called “bridge” to manage the parallel execution of production (business) and update. However ZDO is not enabled for SAP BW yet.

So let’s focus of the pros and cons of the “single system”, “standard” and “advanced” mode of SUM for SAP BW.

What are the benefits of the different SUM modes regarding SAP BW business downtime?

When considering the “advanced” mode:

• Intensive parallelization of processes:  enabled for BW
• nZDM feature of SUM:                        enabled for BW
• import of customer transports:            no support of BW specific transports   

Regarding the downtime minimization for SAP BW updates and upgrades the shadow operation and especially the nZDM feature of SUM advanced mode is in focus.

The SUM procedure in “standard” or “advanced” mode switches the system to the maintenance mode during the upgrade procedure. This means at this time the LOCK_EU locks the Workbench and transports. Additionally the customizing is locked as well.

Latest when SUM is in the maintenance mode any BW activity that requires the change of dictionary objects in the background will be unavailable.  When the maintenance mode of SUM is set the upgrade will switch the BW automatically to “non-changeable”.

This is depending on the SUM mode you use:

• “single system” mode: phase LOCKEU_PRE
• “standard” or “advanced” mode: phase REPACHK2

When the entire BW system is set “non-changeable”, only certain types of BW objects for which this is explicitly allowed will be changeable. (refer to SAP Note 337950).

Considering all these restrictions the shadow phase of SUM might be considered as similar to downtime by BW customers. Hence, you might ignore the downtime minimization features in SUM for your SAP BW because the restrictions are not acceptable. Also, the shadow activities extend the overall runtime of the SUM.

In summary, the most important downtime for BW customers is any time in which query execution or data loading is limited or unavailable in the BW system – something that is technically not feasible during the extended maintenance phase because of using the nZDM option.

Therefore, the recommended SUM mode for SAP BW might be the “single system” mode because of the relatively short overall runtime.