The ‘format’ utility has a new feature beginning in Solaris 10 6/06 Operating System called ‘in use checking’.
This feature is enabled by default.
Any time the ‘format’ utility is run on the disk, it performs many verification/checks on the disk itself (does it contain a slice that is mounted, is it part of SVM metadevice, is it being used by ZFS filesystem, is it being used by swap etc…)
So, to avoid this kind of situation, there is an environment variable ‘NOINUSE_CHECK’ which can be set / turned on, prior of running the ‘format’ command:
Once that is set, the ‘format’ command will proceed with no time by passing all of the verifications and checking.