End mirroring
When you end mirroring for a dbspace, blobspace, or sbspace, the database server immediately releases the mirror chunks of that space. These chunks are immediately available for reassignment to other storage spaces.
Only users informix and root on UNIX™ or members of the Informix-Admin group on Windows™ can end mirroring.
You cannot end mirroring if any of the primary chunks in the dbspace are down. The system can be in online mode when you end mirroring.