Sunday, November 20, 2011

Shadow system / instance and system switch

If you ever worked for SAP upgrade project you probably already came across to this term – shadow system or instance and system switch. What is that? Let me first introduce background of upgrades. Basically by upgrade we want to get the newest functions that provider offers in its software product that we are currently using. For sure we want to get this done without an interruption to existing, running system. In reality there is always some interruption. We are just trying to minimize it as much as possible. So does the SAP. The background of shadow system is to minimize system downtime during the upgrade.

Shadow system is basically copy of system that is going to be upgraded. This copies system is a bit limited to original one. It has only technical repository (SAP Basis objects) of objects and you cannot run your business processes on it.  More over technical repository is upgraded into version of final release of to be upgraded system. Technically speaking it is used for modification adjustments (famous transactions SPAU and SPDD) and activation of objects. All the support packages and add-ons are imported into this instance as well. By them you get you system to the higher release. Let me mention also that shadow system run in the same database as its original system. They are running in parallel.

During preparation of shadow instance you are still running your original SAP system where all the business processes are being executed normally. At the moment when shadow instance is prepared we do its switch from shadow to original system. This is called system switch when you kind of “exchange” original system with shadow one. By that time shadow system becomes upgraded system. 

By using this approach you can minimize downtime of your production system and also you do not have to have additional hardware resource for creation of shadow instance as it runs in the same database and application server as original system.
Notice that a matter of SAP system is very complex all the information provided can serve as very brief introduction into this topic. I wish you a lot of successful upgrade projects.

More on this topic:
Different SAP upgrade tools

2 comments:

Anonymous said...

good

Prakash Tiwari said...

that was very helpful..thats exactly what my senior told me about shadow instance today :)