DSNM100I SUBSYSTEM xxxx NOT AVAILABLE

Explanation
 The IMS TM command
facility which routes commands to the Db2 subsystem
cannot perform its functions because the Db2 subsystem
named 'xxxx' is considered not operational.

System action
 The connection to the Db2 subsystem failed for the command. The command
is rejected.

System programmer response
 If the Db2 subsystem is operational, and if you suspect an
error in Db2, you might need to report the problem.For information about identifying and reporting the
problem, see Collecting diagnostic data. The
person entering the request may not be authorized to execute the command.
If the Db2 subsystem is not
operational, Db2 commands from IMS TM cannot
be processed.

Problem determination
 A snap record (X'5501FF') is written
to the IMS TM log
if a connection request failed.