I am not going to be detailed as there are lots of discussion on 11g Upgrade, yet I want to share my experience.
I work on a warehouse environment with discoverer as the reporting tool. ASM is used for storage management.
So there are four databases on one server to be upgraded.
Warehouse Design Repository Database
Application Server Metadata Repository
Interestingly and commonly all the database has to be upgraded in a short time frame to minimizing the downtime.
Note: All the database has been individually tested and so I had an option to bundle them into one upgrade window.
So here are few tips that I took to reduce the downtime
Operating System , I made sure that the OS patches and kernel are properly set on a separate weekend.
Space , I made sure that there is enough space for the new oracle homes.
Software , Base 220.127.116.11 , Upgrade Patchset 18.104.22.168 and PSU October 2009 is properly staged.
A day before the upgrade downtime
I create the directory structures for the 4 oracle home
Installed 22.214.171.124 into the ASM Home.
Upgraded the ASM Home to 126.96.36.199
Installed PSU Patch Setup Update which also includes the latest CPU to the ASM Oracle Home.
Ran the Pre-Upgrade Scripts and took necessary action.
Prepared a checklist for re-checking the same during upgrade window.
For the other Oracle Home I cloned the ASM Home by following the cloning procedure , there by saved a lot of time. The ASM Home had the latest patchset and PSU update , so it was handly and contacted once to run all the root.sh by the unix administrator.
The Upgrade Day
So , 50% of my work was done , i.e, I have all my Oracle Home with latest patchset updates ready for upgrade.
Reverified Pre-Upgrade Scripts
Backed Up the Databases
First I started with the ASM migration with DBUA
Then I started DBUA from three different VNC Server for the 3 Oracle Home and upgraded three of them in parallel.
Note: During Upgrade I opted to switch of archival and flashback.
Performed Post Upgrade necessary task.
My server had enough CPU and Memory to support the parallelism and so I did , please do not upgrade in parallel if the hardware is less resourced.
Summary of key areas of reducing the downtime window:
- Prepare the Operating System in advance.
- Prepare the 11g Oracle Home in advance.
- Use Oracle Home cloning procedure to reduce the effort.
- Upgrade all the Database in Parallel
- Switch off archival and flashback in the DBUA wizard.
Overall I had a peaceful upgrade to 11g R1. I hope this helps.