Upgrade from 8.1.6 to 8.1.7

[lesstjm]

We are thinking of upgrading our database from 8.1.6 to 8.1.7. We have 6 databases on one server, can we upgrade one at a time or do we have to upgrade all of them at the same time?

[rcaballe]

If you upgrade the ORACLE_HOME which the DB starts from, then you must upgrade the DB before use it.
In Unix you can maintain 2 or more ORACLE_HOMEs and then select which will start what. (In NT also but I guess it is more difficult)