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What are the main differences to the standard procedure

Here is the simplified standard procedure to patch an Abap stack:

– backup and stop the system (deactivate jobs and lock users)
– apply the new kernel
– restart the system
– apply the latest SPAM/SAINT update
– apply support packages (with SPDD)
– SPAU / SGEN
– release system for “production” (activate jobs and unlock users)

Obviously the system is not available for the users the whole time. With the downtime minimized option we can import the DDIC objects at uptime. Here is the procedure how i do it:

– (online backup)
– apply only tp/R3trans (SAPCAR -xvf SAPEXE.SAR tp R3trans)

– apply the latest SPAM/SAINT update
– inactive import: start support packages (with SPDD)
– stop system (deactivate jobs and lock users) -> downtime starts here

– apply the new kernel
– resume support packages until the downtime phase ends
– start system, complete support packages

– SPAU, SGEN
– release system for “production” (activate jobs and unlock users)

Test Details

SAP ERP 6.0 Stack 10
HP-UX IA64 11.23, 4CPU, 16GB, Disks HP EVA 5000
Oracle 10.2.0.2, Noarchivelog during downtime phases, DB size 200gb
applied full Stacks 11 – 14, total 160 packages

Results

standard method (db_cache_size=2000M): 10.5h
Downtime minimized (db_cache_size=2000M): 7h      
Downtime minimized (db_cache_size=500M): 9h
standard method (db_cache_size=500M): estim > 12h

Conclusions

Overall was possible to reduce the downtime phase roughly by 30%. The downtime minimized procedure seemed stable and did not add more complexity.

When i analyzed the workload during the first test, i learned that we spent a significant amount of time with disk io on tables which were mostly dictionary tables, for example DD03L and DDNTF. In a ERP system the size of these tables including indices exceeds 3gb. As this was only a smallish test system we only had a database buffer (db_cache_size) of 500M. This lead to low cache hit ratio in almost all phases. For example the DDIC_ACTIVATION took 2hrs with a 500M buffer and only 1.5hrs with 2000M.

Links, docu, blogs on the downtime minimized option

SDN Blogs:
How to Apply Support Packages while Reducing Downtime

Applying Support Package Stacks Made Easy

help.sap.com:
SPAM/SAINT Import Mode: Downtime-Minimized

Support Package Stack Guide: service.sap.com/instguides -> SAP NetWeaver -> SAP NetWeaver 7.0 -> Maintenance

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