Taken from GPFS Administration and Programming Reference – Enabling and disabling GPFS quota management

To enable GPFS quota management on an existing GPFS file system

1. Unmount the file system everywhere.
2. Run the mmchfs -Q yes command. This command automatically activates quota enforcement whenever the file system is mounted.
3. Remount the file system, activating the new quota files. All subsequent mounts follow the new quota setting.
4. Compile inode and disk block statistics using the mmcheckquota command. The values obtained can be used to establish realistic quota values when issuing the mmedquota command.
5. Issue the mmedquota command to explicitly set quota values for users, groups, or filesets.

Once GPFS quota management has been enabled, you may establish quota values by:

1. Setting default quotas for all new users, groups of users, or filesets.
2. Explicitly establishing or changing quotas for users, groups of users, or filesets.
3. Using the gpfs_quotactl() subroutine.

To disable quota management:

1. Unmount the file system everywhere.
2. Run the mmchfs -Q no command.
3. Remount the file system, deactivating the quota files. All subsequent mounts obey the new quota setting.

To enable GPFS quota management on a new GPFS file system:

1. Run  mmcrfs -Q yes command. This option automatically activates quota enforcement whenever the file system is mounted.
2. Mount the file system.
3. Issue the mmedquota command to explicitly set quota values for users, groups, or filesets. See Explicitly establishing and changing quotas.