You'll get better input if you give a little more information.  What level
ADSM or TSM?  What level client?

A while ago I had similar problems with Solaris clients hanging in the
middle of thier sessions.  If they were writting to tape then they would
hold onto them until I restarted the server.  This was under ADSM 3.1.50 on
AIX.  I was able to solve it by bringing the server up to level 3.1.55.
That cured it for me.

Jack