It means that you are experiencing escalation from row level locks to table level locks, usually because you are running short of storage for locks (locklist parm). You should probably increase your locklist parm, and maybe the maxlocks (the percent of the locklist that can used by any one application before escalation occurs).
If you dont have contention (lock timeouts or deadlocks) keep in mind that lock escalation can sometimes be a good thing because DB2 will spend less time locking at the table level than having to lock each individual row.
M. A. Feldman
IBM Certified DBA on DB2 for Linux, UNIX, and Windows
IBM Certified DBA on DB2 for z/OS and OS/390