DB2 trigger after update, update singl;e column n the updated row in the same table

Using DB2 on cloud ( LUW )
I want to update a single column value in a row, after any of the other values in that row get updated.

The following AFTER INSERT works

CREATE TRIGGER CENTRAL_REPOSITORY.TR_DATABASE_OBJECT_INS_CDT
 AFTER INSERT ON CENTRAL_REPOSITORY.DATABASE_OBJECT
 REFERENCING NEW AS N_ROW
 FOR EACH ROW
 UPDATE CENTRAL_REPOSITORY.DATABASE_OBJECT SET create_datetime = current_timestamp
 	where id = N_ROW.id

The following AFTER UPDATE does not

CREATE TRIGGER CENTRAL_REPOSITORY.TR_DATABASE_OBJECT_UPD_UDT
 AFTER UPDATE ON CENTRAL_REPOSITORY.DATABASE_OBJECT
 REFERENCING NEW AS N_ROW
 FOR EACH ROW
 UPDATE CENTRAL_REPOSITORY.DATABASE_OBJECT SET update_datetime = current_timestamp
 	where id = N_ROW.id;

The error I get after trying to run an insert on the table is

"An error occurred in a triggered SQL statement in trigger "CENTRAL_REPOSITO". Information returned for the error includes SQLCODE "-724", SQLSTATE "54038" and message tokens "CENTRAL_REPOSITORY.TR_DATABASE_OBJECT_UPD_".. SQLCODE=-723, SQLSTATE=09000, DRIVER=4.32.28"

You shouldn't be using an AFTER trigger,

Use a BEFORE trigger...

CREATE TRIGGER CENTRAL_REPOSITORY.TR_DATABASE_OBJECT_UPD_UDT
 BEFORE UPDATE ON CENTRAL_REPOSITORY.DATABASE_OBJECT
 REFERENCING NEW AS N_ROW
 FOR EACH ROW
  SET n_row.update_datetime = current_timestamp;

CREATE TRIGGER CENTRAL_REPOSITORY.TR_DATABASE_OBJECT_UPD_UDT
 BEFORE INSERT ON CENTRAL_REPOSITORY.DATABASE_OBJECT
 REFERENCING NEW AS N_ROW
 FOR EACH ROW
  SET n_row.update_datetime = current_timestamp;

EDIT
You might consider defining the column a "row change timestamp", then you won't need to bother with the triggers at all.

You get this error (SQLCODE = -724) also known as "SQL0724N" when Db2 finds more than one object might get activated if your trigger fires, typically because you have other triggers or RI on the table whose conditions are not mutually exclusive or may cause recursion.

Look at the docs

which includes the following advice:

> Explanation
>
> Cascading of indirect SQL occurs when a trigger activates another
> trigger (possibly through referential constraint delete rules) or a
> routine, containing SQL, invokes another routine. The depth of this
> cascading is limited to 16 for triggers and 64 for routines.
>
> Note that recursive situations where a trigger includes a triggered
> SQL statement that directly or indirectly causes the same trigger to
> be activated, or where a routine directly or indirectly invokes
> itself, is a form of cascading that is very likely to cause this error
> if there are no conditions to prevent cascading from exceeding the
> limit.
>
> The object-type is one of TRIGGER, FUNCTION, METHOD, or PROCEDURE.
>
> The object-name specified is one of the objects that would have been
> activated at the seventeenth level of cascading.

> User response
>
> Start with the objects that are activated or invoked by the statement
> that received this error. If any of these objects are recursive,
> ensure that there is some condition that prevents the object from
> being activated or invoked more than the limit allows. If this is not
> the cause of the problem, follow the chain of objects that are
> activated or invoked to determine the chain that exceeds the cascading
> limit.