>When upgrading from 3.7.2 to 3.7.4 it gave Following  messages
>i am using ACSLS 5.3.0. seems to be drive related error.
>
...
>
>lsdev: 0514-521 Cannot find information in the predefined device
>        configuration database for the customized device mt0.

This AIX message is obliquely saying that the device driver is not installed
for the device.  Go into SMIT and have a look around.
The classic problem with 'mt' devices is that they are the *SM name for
devices which are also known to the operating system as 'rmt' devices;
and if the operating system goes at them first, it gets them and in effect
takes then away from *SM.
     Richard Sims, BU