First Improved Example
The first method of improving the performance of this RDML program by using working lists involved loading the entire STATES file into a list when the program first starts and then replacing the FETCH command with a LOC_ENTRY command:
GROUP_BY NAME(#TRANS) FIELDS(#TRANNUM #TRANDATE #TRANTIME
#TRANTYPE #TRANDESC #TRANUSER #TRANSTATE #STATDESC)
DEF_LIST NAME(#STATES) FIELDS(#STATCODE #STATDESC)
TYPE(*WORKING) ENTRYS(10)
SELECT FIELDS(#STATES) FROM_FILE(STATES)
ADD_ENTRY TO_LIST(#STATES)
ENDSELECT
SELECT FIELDS(#TRANS) FROM_FILE(TRANS)
LOC_ENTRY IN_LIST(#STATES) WHERE('#STATCODE = #TRANSTATE')
FETCH FIELDS(#TRANS) FROM_FILE(TRNTYP)
WITH_KEY(#TRANTYPE)
UPRINT FIELDS(#TRANS)
ENDSELECT
In the case where file TRANS contained 10,000 records and file STATES contained 6 records, this program would now do (10,000 + 6 + 10,000) = 20,006 database accesses, a net improvement of 9,994 less I/Os. The run time would probably be about 2/3 of the original version of the program.