Your system must be in restricted mode (ENDSBS *ALL). Your users will be off, also all your scheduled jobs will be on hold. When the command is done, you will have to manually start all the scheduled jobs that would have run during that time.
I used to run the command bi-annually, but stopped about 4 releases ago. The reason: it never “reclaimed” any lost storage. If an object is reported “damaged”, delete it and restore it from backup.