There are several reasons for lock escalation. One reason may be that the locklist parameter is running out of memory for additional row level locks. You might want to increase the size of the locklist to prevent escalation because of memory problems.
Another reason for escalation is if one application has more than a certain percentage of the locks in the locklist. This is controlled by the maxlocks parameter.
The message you got about getting "1" table level lock is not related to the number of other locks that may have caused the escalation.
Check the "Administration Guide: Performance" for more information on these parameters.
M. A. Feldman
IBM Certified DBA on DB2 for Linux, UNIX, and Windows
IBM Certified DBA on DB2 for z/OS and OS/390