More Efficient Example
This program is functionally identical to the first example, but produces the same results in a much shorter time and with less use of computer resources. New or modified commands are indicated by ->.
******** Define work variables and browse list to be used
DEFINE FIELD(#L1COUNT) TYPE(*DEC) LENGTH(7) DECIMALS(0)
-> DEFINE FIELD(#L1PAGE) TYPE(*DEC) LENGTH(7) DECIMALS(0)
-> DEFINE FIELD(#L1TOP) TYPE(*DEC) LENGTH(7) DECIMALS(0)
-> DEFINE FIELD(#L1POS) TYPE(*CHAR) LENGTH(7)
-> DEF_LIST NAME(#L1) FIELDS((#SURNAME) (#GIVENAME) (#EMPNO)
(#ADDR ESS1)) COUNTER(#L1COUNT) PAGE_SIZE(#L1PAGE)
TOP_ENTRY(# L1TOP) SCROLL_TXT(#L1POS)
******** Loop until terminated by EXIT or CANCEL
BEGIN_LOOP
******** Get surname to search for
REQUEST FIELDS(#SURNAME)
******** Build list of generically identical names
CLR_LIST NAMED(#L1)
-> CHANGE FIELD(#IO$KEY) TO(UP)
-> CHANGE FIELD(#L1TOP) TO(1)
-> SELECT FIELDS(#L1) FROM_FILE(PSLMSTV1)
WITH_KEY(#SURNAME) GENERIC(*YES)
-> WHERE('#IO$KEY = UP') OPTIONS(*ENDWHERE)
-> EXECUTE SUBROUTINE(DISPLAY) WITH_PARMS('''More...''')
ADD_ENTRY TO_LIST(#L1)
ENDSELECT
******** If names found, display list to user
IF COND('#L1COUNT *GT 0')
-> EXECUTE SUBROUTINE(DISPLAY) WITH_PARMS('''Bottom''')
******** else issue error indicating none found
ELSE
MESSAGE MSGTXT('No employees have a surname matching
request')
ENDIF
******** Loop back and request next name to search for
END_LOOP
********
******** Display names if page is full or list is complete
********
-> SUBROUTINE NAME(DISPLAY) PARMS(#L1POS)
-> DEFINE FIELD(#L1REMN) TYPE(*DEC) LENGTH(5) DECIMALS(5)
-> CHANGE FIELD(#L1REMN) TO('#L1COUNT / #L1PAGE')
-> IF COND('(#L1COUNT *NE 0) *AND
(#IO$KEY = UP) *AND
((#L1POS = ''Bottom'') *OR
(#L1REMN *EQ 0.00000))')
-> DOUNTIL COND('(#L1POS *NE ''Bottom'') *OR
(#IO$KEY *NE UP)')
-> DISPLAY BROWSELIST(#L1) USER_KEYS((*ROLLUP))
-> ENDUNTIL
-> CHANGE FIELD(#L1TOP) TO('#L1TOP + #L1PAGE')
-> ENDIF
-> ENDROUTINE
The "page at a time" technique described here can be applied to just about any situation where a browse list is to be displayed and can considerably improve performance in most of them.
It is easy to modify existing programs that use SELECT and DISPLAY (like the initial example here) to use the page at a time technique. Note how the new logic "slots into" the existing logic with no major structural change to the program logic/flow.
The easiest way to implement "page at a time" techniques is to design and fully test a standard "algorithm" that is suitable for your site's needs. This can then be used as a base or template for all future applications.