Did you ever change lock_sga = true for an Oracle Instance on AIX 5.3, and did see
ORA-27126: unable to lock shared memory segment in core IBM AIX RISC System/6000 Error: 1: Not owner
Do the following:
# vmo -o v_pinshm v_pinshm = 0 # vmo -o v_pinshm=1 Setting v_pinshm to 1 # lsuser -a capabilities oracle oracle # chuser capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE oracle # lsuser -a capabilities oracle oracle capabilities=CAP_BYPASS_RAC_VMM,CAP_PROPAGATE
It should do now.