8.1 FP11 on AIX 5.3.

The following DELETE is poorly performing and causing lock escalation
(and subsequent deadlock time-outs):

DELETE FROM submission_log
WHERE subm_id = ?
OR subm_id = (SELECT orig_subm_id FROM submission WHERE subm_id = ?)

Optimizer Plan:

DELETE
( 2)
/------------/ \---\
NLJOIN
Table:
( 3)
/----------------/ \---------------\
SUBMISSION_LOG
FETCH FETCH
( 4) (----)
/ \ /--------/ \
IXSCAN Table: RIDSCN
Table:
( 4) ( 7)

| SUBMISSION /--------/ \--------\
SUBMISSION_LOG
Index: SORT SORT
( 8) ( 10)
PK_SUBMISSION | |
IXSCAN IXSCAN
( 9) ( 11)
/ \ / \
Index: Table: Index: Table:
I_SUBM_LOG_S_A SUBMISSION_LOG I_SUBM_LOG_S_A
SUBMISSION_LOG


Can anyone provide (SQL?) tips other than to increase LOCKTIMEOUT,
LOCKLIST that might improve matters?

Many thanks.