run 8.0.5.1 on Sco Unixware 7.1.1

THIS IS ERROR FROM ALERT.LOG --

Thu Mar 22 23:36:24 2001
Errors in file /ora/app/oracle/admin/DBU4/bdump/snp0_dbu4_7722.trc:
ORA-12012: error on auto execute of job 100
ORA-12008: error in snapshot refresh path
ORA-04030: out of process memory when trying to allocate 52356 bytes (pga heap,ksm tack)
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 386
ORA-06512: at "SYS.DBMS_IREFRESH", line 450
ORA-06512: at "SYS.DBMS_REFRESH", line 182
ORA-06512: at line 1

I had the same error before so I shutdown instance and restart on 17:06:17 only takes 6.5 hours it happens again.
my ulimit=2113674

Could you please let me know how to solve it?

thanks