Another post about some of the finer points for the internals functions available in the 2e tool. I have covered off the RTVOBJ and CRTOBJ in some detail. I have left the obvious stuff for the user manuals and am really covering off best practices and gotchas in these sections.
Any observations and comments are gratefully received and a big shout out to Ray Weekes who passed on many of these in these sections from his experience.
The default CHGOBJ will have all parameters open except for Time Stamp and any other derived attributes which will all be made NEITHER. Action diagram coding added will only be for Time Stamp and derived data i.e. Audit records or calculated values.
Further CHGOBJ functions may be created where only subsets of attributes are to be changed or where special processing is applicable. All CHGOBJs should replicate the standard support for Time Stamp and derived data where appropriate.
Structuring your parameters. There are 2 methods for defining a CHGOBJ where only subsets of attributes are to be changed. The default method uses the UPD ACP RCD defined over the first parameter block line as the input parameter list. Database attributes not to be automatically changed from input parameter fields are set to NEITHER.
The second method uses the UPD ACP KEY as the first input parameter list line. The UPD ACP RCD is then optionally used on the second parameter line. This second approach suppresses any automatic update to the DB1 context and therefore requires a *MOVE ALL PAR to DB1 to be added to USER:After DBF Read. This KEY method has the advantage that no NEITHER parameters need be defined and no unnecessary coding is generated for NEITHER parameters.
It also protects the CHGOBJ from the effects of future attributes being added to the file.
The default RCD method of a defining CHGOBJ is sufficient for most small files or where most attributes are being replaced. The KEY method is preferred for large files where only a few attributes are being changed. It is also the preferred method on any file where existing database attributes are being incremented rather than replaced with new parameter input values since it makes the action diagram coding simpler. E.g. A CHGOBJ designed to get the next surrogate# to be used.
General pointers.
It is possible to suppress the default error message if the record does not exist by setting PGM.*Return Code = *Normal in USER:Record Not Found. Alternatively you may add a call to a CRTOBJ over the same file. But if the CRTOBJ is conditional then still set PGM.Return Code = *Normal where CRTOBJ is not called.
Any UPD ACP RCD parameter field defined as OUPUT or BOTH will be automatically moved from DB1 context to PAR context after the database update. This allows a CHGOBJ to also function like a RTVOBJ GET and to return current database values.
When using a CHGOBJ to increment values on a database remember to move the current DB1 values to a holding field as the PAR to DB1 move will overwrite the original values. Then in the Process before Update you do the *ADD arithmetic. A good standard could be to prefix the function like UPD nnnnnnnnnnnnnn.
Null update suppression is the preferred choice for all CHGOBJs. Model value YNLLUPD=*AFTREAD. This means that an image check takes place after USER:After DBF Read. The USER: Before DBF Update is only executed if the record image has been changed. Time Stamp logic and other derived processing must therefore be in USER: Before DBF Update.
In general do not use a CHGOBJ to change the primary key. Although this technique works in RPG it causes problems in COBOL. However, it may be used in RPG & SQL. SQL CHGOBJ requires the key fields to be set to MAP to force them into the SET clause.
Gotcha's
You must never *QUIT from a CHGOBJ since this may leave a lock on the record. Use PGM.*Record Changed = *Yes if any conditional processing is required inside the CHGOBJ.
Do not use a CHGOBJ or DLTOBJ over a PHY ACP because of a bug in the 2E SQL generator.
Any observations and comments are gratefully received and a big shout out to Ray Weekes who passed on many of these in these sections from his experience.
The default CHGOBJ will have all parameters open except for Time Stamp and any other derived attributes which will all be made NEITHER. Action diagram coding added will only be for Time Stamp and derived data i.e. Audit records or calculated values.
Further CHGOBJ functions may be created where only subsets of attributes are to be changed or where special processing is applicable. All CHGOBJs should replicate the standard support for Time Stamp and derived data where appropriate.
Structuring your parameters. There are 2 methods for defining a CHGOBJ where only subsets of attributes are to be changed. The default method uses the UPD ACP RCD defined over the first parameter block line as the input parameter list. Database attributes not to be automatically changed from input parameter fields are set to NEITHER.
The second method uses the UPD ACP KEY as the first input parameter list line. The UPD ACP RCD is then optionally used on the second parameter line. This second approach suppresses any automatic update to the DB1 context and therefore requires a *MOVE ALL PAR to DB1 to be added to USER:After DBF Read. This KEY method has the advantage that no NEITHER parameters need be defined and no unnecessary coding is generated for NEITHER parameters.
It also protects the CHGOBJ from the effects of future attributes being added to the file.
The default RCD method of a defining CHGOBJ is sufficient for most small files or where most attributes are being replaced. The KEY method is preferred for large files where only a few attributes are being changed. It is also the preferred method on any file where existing database attributes are being incremented rather than replaced with new parameter input values since it makes the action diagram coding simpler. E.g. A CHGOBJ designed to get the next surrogate# to be used.
General pointers.
It is possible to suppress the default error message if the record does not exist by setting PGM.*Return Code = *Normal in USER:Record Not Found. Alternatively you may add a call to a CRTOBJ over the same file. But if the CRTOBJ is conditional then still set PGM.Return Code = *Normal where CRTOBJ is not called.
Any UPD ACP RCD parameter field defined as OUPUT or BOTH will be automatically moved from DB1 context to PAR context after the database update. This allows a CHGOBJ to also function like a RTVOBJ GET and to return current database values.
When using a CHGOBJ to increment values on a database remember to move the current DB1 values to a holding field as the PAR to DB1 move will overwrite the original values. Then in the Process before Update you do the *ADD arithmetic. A good standard could be to prefix the function like UPD nnnnnnnnnnnnnn.
Null update suppression is the preferred choice for all CHGOBJs. Model value YNLLUPD=*AFTREAD. This means that an image check takes place after USER:After DBF Read. The USER: Before DBF Update is only executed if the record image has been changed. Time Stamp logic and other derived processing must therefore be in USER: Before DBF Update.
In general do not use a CHGOBJ to change the primary key. Although this technique works in RPG it causes problems in COBOL. However, it may be used in RPG & SQL. SQL CHGOBJ requires the key fields to be set to MAP to force them into the SET clause.
Gotcha's
You must never *QUIT from a CHGOBJ since this may leave a lock on the record. Use PGM.*Record Changed = *Yes if any conditional processing is required inside the CHGOBJ.
Do not use a CHGOBJ or DLTOBJ over a PHY ACP because of a bug in the 2E SQL generator.
Next time the DLTOBJ.
Thanks for reading.
Lee.
Thanks for reading.
Lee.
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