On the Lou mass storage system, the Data Migration Facility (DMF) manages disk space by moving unused files to storage on tape.

Use the dmls command on Lou to determine whether a file is on tape or disk. The output shows the state of each file. For example:

lou dmls -l
total 220
-rw-r-----   1 aeneuman madmag      20155 Mar  2 11:24 (REG) A
-rw-r-----   1 aeneuman madmag    1209300 Mar  3 11:24 (OFL) B
-rw-r-----   1 aeneuman madmag     201550 Mar  3 11:18 (DUL) C

In this example:

• File A is in REG (regular) state, which indicates it is on disk
• File B is in OFL (offline) state, which indicates it is on tape
• File C is in DUL (dual) state, which indicates that identical copies of the file exist on both disk and tape

When a file is in dual state, the online (disk) copy will persist if there is no demand for free space in its filesystem. When free space is needed, the online copy of the file is removed, leaving just the offline copy—in this case, the file state will change from DUL to OFL. If you make any change to a dual-state file, the offline copy becomes out of date and invalid—in this case, DMF will treat it as a completely new file and the file state will change from DUL to REG.

For a list of other possible file states, see Data Migration Facility (DMF) Commands.