COBOL question, believe it or not!

[jtemple]

For various reasons, I find myself needing to learn some COBOL. I have a question about key fields when using the "START" statement. When I compile my program using this START:

START WFTINL09                                               
      KEY IS EQUAL TO SV-LDWHS, SV-LDASLE, SV-LDBAY, SV-LDLVL
   INVALID KEY SET WFTIN-END-OF-FILE TO TRUE.

I get the following message in the compile:

MSGID: LNC0635  SEVERITY: 20  SEQNBR:  004601                        
Message . . . . :   Keys specified do not match externally-described 
  keys for file 'WFTINL09'. KEY IS phrase ignored.

Now the SV-* fields are defined with the exact same attributes as the key fields in the file (they are all 3 character). My program produces no output when START is specified like this.

When I changed this to:

MOVE SV-LDWHS TO TIWHS.                          
MOVE SV-LDASLE TO TIASLE.                        
MOVE SV-LDBAY TO TIBAY.                          
MOVE SV-LDLVL TO TILVL.                          
START WFTINL09                                   
      KEY IS EQUAL TO TIWHS, TIASLE, TIBAY, TILVL
   INVALID KEY SET WFTIN-END-OF-FILE TO TRUE.

I don't get the previously mentioned message in the compile and the program produces the output I expect. The only difference between the two is the TI* names come from WFTINL09. This tells me that you have to use the names of the key fields from the database file when using START? Being an old RPG guy, I'm used to using whatever field names I want, as long as the field matches the attributes of the file's key fields.

[Terry Wincheste]

Re: COBOL question, believe it or not!

Cobol is based on international standards, hence the need to explicitly define the keys on a START statement Its best to initialize the key values with your data structure values (e.g. working-storage variables) and then use the following syntax:

start WFTINL09 key >= externally-described-key 
    invalid key
        perform Error-Processing here...
end-start

BTW, if your looking for equality, its best to just use a READ statement after setting up your key values. It looks like your trying to emulate SETLL, if so, then use the >= operator to position your record pointer, READ the record and then compare one or more key values to ensure you have got the right record entry. Unlike RPG, there is no READE using partial key values, you must do an IF comparison to determine if you have read the correct record.

Terry

[jtemple]

Re: COBOL question, believe it or not!

Cobol is based on international standards, hence the need to explicitly define the keys on a START statement Its best to initialize the key values with your data structure values (e.g. working-storage variables) and then use the following syntax:

start WFTINL09 key >= externally-described-key 
    invalid key
        perform Error-Processing here...
end-start

Terry

Well, the one thing I forgot to mention is that this is a START with a partial key. I can't use externally-described-key for that, right? Also, could you maybe provide a mock-up example of initializing key values with DS values? I'm not sure I'm following you.

Thanks!

[Terry Wincheste]

Re: COBOL question, believe it or not!

I can't use externally-described-key for that, right?

Sure you can! Assuming the WFTINL09 file is defined with the following keys:

	TIWHS
	TIASLE                        
        TIBAY                          
        TILVL

Then the following pseudo-code will position the record pointer using the START keyword with the partially filled key values, READ the record into the file record buffer and then check to ensure that we have a match of values on our partial key values. Note the >= being used for our comparison operator...

move SV-LDWHS   to TIWHS                          
move SV-LDASLE  to TIASLE                        
move spaces     to TIBAY                          
move spaces     to TILVL                          
start WFTINL09 key >= externally-described-key
   invalid key
	set WFTIN-END-OF-FILE to TRUE 
end-start

read WFTINL09 next        
    at end                         
        set WFTIN-END-OF-FILE to TRUE
end-read

if  SV-LDWHS  = TIWHS                          
and SV-LDASLE = TIASLE
    First two key values are equal!
else
    Oops...partial key values are not equal
end-if

Hope this is a little clearer

Terry

[jtemple]

Re: COBOL question, believe it or not!

So can I also assume there is no COBOL equivalent of RPG's READE?

[Terry Wincheste]

Re: COBOL question, believe it or not!

So can I also assume there is no COBOL equivalent of RPG's READE?

Your assumtion is correct In effect, READE in RPG automagically checks the partial key values behind the scenes so that the programmer doesn't have to write the code

RPG is the only language I know where file positioning (SETLL) and read statements (READx) permit partial key matching without the use of additional HLL statements.

Terry