Re: Output of Null-Capable Fields in the Trigger Buffer

Take a look at the catalog files.  QADBIFLD,  if memory serves, gives a
listing of the fields and their positions, sizes, etc.

----- Original Message -----
From: "Alexander Brand" <Brand@ireks.com>
To: <RPG400-L@midrange.com>
Sent: Monday, May 22, 2000 3:48 AM
Subject: Output of Null-Capable Fields in the Trigger Buffer


> Hi,
> is there a way to find out the position-number of an field in my
> database file?
>
> I created a before trigger (insert and update) to manipulate
> some fields in our files like ID-Number, WriteDate, WriteTime,
> UpdateDate, Update Time and so on.
>
> But some of these fields are null-capable. When a null-capable field is
> output to or updated in the trigger new record image, then if the
> field is null, the value placed in the buffer will be ignored by data
management.
> These fields have the null indicator on in the trigger new null record
map: This is
> the map of the null record fields of my database file. This character
array has the
> same length as the number of fields in the database file associated to the
trigger
> program. DB2/400 can set each character to 1 (NULL field) or 0 (not NULL).
>
> How can I find out the position of the field in my database file to set
the null
> indicator off? I need a softcoding version because I don t want to
hardcode
> the position number.
>
> In IBM s Redbook "DB2/400 Advanced Database Functions" theres is an
example
> of softcoding the trigger buffer. This means that if for some reason you
change the structure of the
> physical file, you also need to change the structure of the physical file
inside the
> trigger program. This must be repeated for all the trigger programs where
the
> structure of the related table has changed. The alternative is that at the
time of
> writing the trigger program, you do not hard code the structure of the
table but
> soft-code it. That way if and when you change the structure of a table,
you only
> need to recompile the trigger program and not make any changes to the
trigger
> program itself.
>
> Example:
>
> ********************************************************
> * TRIGGER BUFFER data structure
> ********************************************************
> D TgBufDs                DS
> .....
> D TgAftOfs                                         Like( TypeBin4 )
> D TgAftLen                                        Like( TypeBin4 )
> D TgAftNulOf                                     Like( TypeBin4 )
> D TgAftNulLn                                     Like( TypeBin4 )
> D TgBufChr                 1     32767A
> D TgBufAry                                1A    Overlay( TgBufChr )
> D                                                        DIM
%Size( TgBufChr ) )
>
> ***********************************************************
> * Data Structures for the Before and After images
> ***********************************************************
> D BfCustomer E DS ExtName( Customer ).
> D                             Prefix( Bf )
> D                             Based( TgBfrPtr )
> D AfCustomer E DS ExtName( Customer ).
> D                             Prefix( Af )
> D                             Based( TgAftPtr )
>
>
> *****************************************************
> * LETS EVALUATE THE VALUE OF THE POINTERS FOR THE BEFORE
> * AND AFTER IMAGES .
> ***********************************************************
> C Eval TgBfrPtr = %Addr(TgBufAry(TgBfrOfs + 1))
> C Eval TgAftPtr = %Addr(TgBufAry(TgAftOfs + 1))
>
>
> Thanks in advance.
> Alexander.
>
> Alexander Brand
> brand@ireks.com
> http://www.ireks.com
>
>
>
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