This might be old news but I just noticed a real neat event while clearing
a cached disk pool on an AIX TSM 5.1.7.0 server...

So I have a disk pool with some 19 volumes for about 550 GB of storage.

Two migrations were running but I fired off an additional six move data's
to occupy all the tape drives.
I had set all the volumes to read only via a "upd vol * acc=reado
wherestg=<mydiskpool>"
Now, I still had 60% utilized but only 20% migratable and in wanting to not
just sit and twiddle my thumbs, I went to do a move data against one of the
volumes not currently being processed in hopes of clearing the cache
pointers from it.
Remember, I currently have no idea how much is cache and how much is actual
data yet to be migrated to tape...

Upon starting a plain move data back into the same storage pool, which has
all its volumes marked as read-only...
Suddenly ALL the volumes started dropping their "Pct Util" reflected in a
"q vol stg=<mydiskpool>"
Some 330 GB of cache pointers across 19 volumes was cleared in about 30
seconds by that one move data command.

I guess in actually having some real data on that volume, and in wanting to
move it to another volume within that same pool, but not being able to
allocate any space (due to all the volumes marked read-only) triggered the
~cache-master~ to start clearing cache and boy did it !

not what I expected but neat

Dwight