>I'm using a PowerMac 7100 running Mac OS system 7.5 and have version
>2.0.4 of MacTCP running (over a local departmental e'net).  I have 16
>MB of memory (not all being used) and was backing up around 200 MB of
>my hard drive.

>I'm running ADSM 1.1.0.18 (PFT IP20126)

>Our "host" system is running VM/CMS and release 1 of their side of the
>ADSM software.

>Once my system is "hung" it appears that all of my TCP/IP connections
>are dropped (ie.  Mosaic client is hung, Tn3270 client is hung).
>Prior to this event everything seems to be working fine.

Some items for your consideration...

1.  The latest version of MacTCP is 2.0.6.  You can FTP an update
    from the various Apple sites.

2.  The latest ADSM is 1.2.0.4 (I believe).

3.  Since you have 16 meg of memory, I'd run ADSM with a preferred size
    of 3meg.  Also, I'd configure ADSM to have 'SlowIncremental' off
    which means that ADSM will read your disks directory tree into
    memory all at once.  For some reason which now escapes me, I seem
    to prefer that mode.

4.  When any MacTCP application hangs on a Mac, it's VERY likely that
    MacTCP will no longer function.  That goes for other applications
    currently running which use MacTCP and applications that have not
    yet been launched that require MacTCP.

    If you use a freeware init (from Apple) called 'ZapTCP' this will
    help.  Basically, ZapTCP just hangs around and if an application
    is force quit by the user, ZapTCP will clean out the MacTCP streams
    that were in use by the application.  This keeps MacTCP in a clean
    working state.  Other applications using MacTCP should then continue
    to work correctly.  Also, you can successfully launch applications
    that will use MacTCP.  Why apple doesn't make MacTCP part of the
    System software is a puzzle to me.

But I don't really see anything with your configuration that would cause
your Mac to hang.  You might want to run with the Finder's 'About this
Macintosh' window open to monitor how much memory ADSM uses as it runs.
If you turn balloon help on, and point to the ADSM application in the
'About this Mac' window, you will see exactly how much memory it's using.

My configuration is similar to yours, and I run ADSM (not the scheduler)
every night and it never hangs.  Typically I backup 3 drives per night:
one 200 meg, one 500 meg, and one 2gig drive.  Once in a while I change
the name of my hard drives from something like "LaPomme" to "LaPomme.95"
to force a point-in-time full backup.  Even during those times, ADSM
hasn't crashed.