Installing Oracle/SAP over Pre-existing Data files

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This procedure is useful when you need to reinstall the NT or Oracle or SAP
software on an existing SAP db/app server, and
you don't want to waste time with a backup/restore to get your database back. This
procedure assumes that all control file paths start with "oracle" (this is usually
the case):

1. backup all parameter files (e.g. Orant/network/admin, Orant/database,
   /usr/sap/SID/sys/profile)
   
2. reinstall NT (if necessary) and Oracle (if necessary)
   
3. reinstall SAP app server from the kernel CD
   
4. restore all parameter files (e.g. Orant/network/admin, Orant/database,
   /usr/sap/SID/sys/profile)
   
5. rename all "oracle" paths to "oracle0" (e.g. oracle/sapdata1, oracle/mirrlogA)
   
6. reinstall sap db server with "create db" and "link to sapdba"
   options only. This will create the necessary registry keys
   
7. quit program when "Creating database" message appears, because you
   don't need to recreate the database.
   
8. stop all oracle services. Delete all "oracle" folders, and
   rename "oracle0" folders to "oracle"
   
9. reboot the machine.