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Oracle Troubleshooting

ORA-01102: cannot mount database in exclusive mode

Symptom:

When opening or mounting the database, the following error is generated:

ORA-01102: cannot mount database in EXCLUSIVE mode.

Cause:

I have only come across this error when using Oracle Parallel Server (OPS). Here, this error indicates that another instance has already been mounted in exclusive or parallel mode.

Possibly Remedies:

  • Mount the database in parallel mode.
  • Shutdown all other instances before mounting the database in exclusive mode.
  • Try stopping and then restarting the service 'OracleService<SID>'.

This page represents one page of many pages of notes I made whilst working with Oracle 7 through to 10i. I now no longer work with Oracle databases, but hope that these notes will continue to be of benefit to others.

About the author: is a dedicated software developer and webmaster. For his day job he develops websites and desktop applications as well as providing IT services. He moonlights as a technical author and consultant.