They are two mandatory parameters to register pl/sql program ?
--This is used two parameters capture error messages and retcode to capture status throw in log file occured in pl/sql prog

Errbuf - To pass the String value to the Logfile if we register the Procedure
as a concurrent program. We can pass the String value through this parameter
relevant to the context of the program. For example the Value if you want to
verify in the logfile instead of backend data verification. If you print the
message why the program went into exception by giving apt message and call it in
the using the below example

EXCEPTION

WHEN no_data_found THEN

errbuf : 'Customer info not found';

FND_FILE.PUT_LINE(FND_FILE_LOG errbuf);

END;

Retcode - It's to decide how the program should end if certain condition
fails

If we pass retcode as 0 - Successful

1- The program ends with "Warning" in the front end

Any number more than 1- The program end with "Error" in the front end.

For Example on the below condition the program will end with Warning.

EXCEPTION

WHEN no_data_found THEN

retcode : 1;

errbuf : 'Customer info not found';

FND_FILE.PUT_LINE(FND_FILE_LOG errbuf);

END;