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Wednesday, September 16, 2020

CHAIN vs SETLL/READE, What to use & When?

CHAIN vs SETLL/READE:

CHAIN & READE, These are the two Operations that are used to read the data from a database file using a specified Key data. 

SETLL Operation is used to point to the record provided in the Key data. 

How do we use? 

CHAIN:

CHAIN (Search Arguments/Key Fields) FILENAME ;
IF %FOUND(FILENAME) ; 
// Required Program Logic
ENDIF ;

Click Here to find more details about CHAIN.

SETLL/READE:

SETLL (Search Arguments/Key Fields) FILENAME ; 
READE (Search Arguments/Key Fields) FILENAME ;
DOW NOT %EOF(FILENAME) ;
// Required Program Logic
READE (Search Arguments/Key Fields) FILENAME ;
ENDDO ;

SETLL:

SETLL (Search Arguments/Key Fields) FILENAME ; 
IF %FOUND(FILENAME) ;
// Required Program Logic
ENDIF ; 

Click Here to find more details about SETLL/RPGLE.

Now, What to use When? 
  • If the Data base file used has Unique key constraint and/or if only one/first matching record is required by the Program, CHAIN would be the best choice. 
  • If the Data base file used has Unique key constraint and/or if the program only intend to check if matching record is present or not (and doesn't require the data), SETLL would be the best choice (with %FOUND).
  • If the Data base file may have multiple records with specified Search Arguments/Key fields and all records are required to be read, READE would be the best choice in combination with SETLL.

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