In case you have to create an Oracle 10g Enterprise Manager instance from scratch, it is very easy.
- emca -repos create
- emca -config dbcontrol db
If you need to blow away the existing Enterprise Manager configuration, you can either recreate the repository, which will wipe out all the configurations:
- emca -repos recreate
- emca -config dbcontrol db
or, you can recreate just the dbcontrol for an instance:
- emca -deconfig dbcontrol db
- emca -config dbcontrol db
to reuse the port that Oracle Enterprise Manager listens on, you need to specify the DBCONTROL_HTTP_PORT:
% emca -config dbcontrol db -DBCONTROL_HTTP_PORT 1158