From System Generation SYSTEM Statement Parameters Information
Limits the number of record locks that a transaction can concurrently hold. When LOCK is specified, limit-n must be an integer in the range 0 through 2,147,483,647."
Also In the System Generation section on Database Locks
"LOCK LIMIT specifies the maximum number of database locks that can be concurrently held by a transaction. "
Locks Requested will typically be much higher than the number of locks held because doing a FIND/OBTAIN when the area is readied Update (or for area readied Retrieval if sysgen specifies RETRIEVAL LOCK) requests a Shared Lock. As soon as the record currency changes to another record occurrence the SHR lock on the prior record is released.
Update locks are held until COMMIT/FINISH so a task/program that does many updates without COMMITs could amass enough locks to exceed the Lock Limit.