DSNJ336I UNABLE TO ALLOCATE TAPE UNIT FOR conn-id corr-id, x ALLOCATED, y ALLOWED.

Explanation
 An attempt to allocate a tape unit for connection
ID 'conn-id' failed. The current maximum tape unit specified is 'y',
but only 'x' are physically available.

System action
 The 'conn-id corr-id' process is queued until
either an allocated tape unit becomes free or more tape units are
varied online and made available to the Db2 archive
read task.

Operator response
 This situation rectifies itself over time
as currently allocated tape units become available. To improve throughput,
vary additional tape units online and make them available to Db2.  Note that a queue rescan is
not attempted until the -SET ARC READ COUNT command is issued or when
an allocated tape dismounts.