Re: Forms 4.0: Global versus Parameter Lists

AMIN -- There is no *one* right way to use either, but here are some

        guidelines that might help you decide:

     Datatype: Globals are on CHAR data

               Parameters are NUMBER, CHAR, or DATE

      Storage: Globals each take about 260 bytes, regardless of length

               Parameters take what they need.

     Creation: Globals are created the first time they are assigned.

	       Parameters must be named and typed at design time, or
	       alternately may be added to a parameter list at runtime
	       with the Add_Parameter() built-in.

      Default: Globals must have a default value programmatically
      Values   assigned.

	       Parameters can be assigned a default value of the
	       proper datatype at design time.

   Assignment: Globals are assigned directly thru PL/SQL assignment
	       with the bind variable notation (:GLOBAL.GLOBAL_NAME),
	       or indirectly with the Copy() built-in.

	       Parameters in the default parameter list (those created
	       at design time) are assigned directly thru PL/SQL with
	       the bind variable notation (:PARAMETER.PARAM_NAME),
	       indirectly with the Copy() built-in. If part of a
	       parameter list which is not the default parameter list,
	       then the Set_Parameter_Attr() built-in is used. In
	       addition, parameters which are declared at design time
	       can be supplied with values on the command line using
	       the "PARAMNAME=Value" syntax.

    Reference: Globals can be referenced directly with bind variable
	       notation, or indirectly with the Name_In() built-in.

	       Parameters in the default parameter list may be
	       referenced directly with bind variable notation, or
	       indirectly with the Name_In() built-in. If part of a
	       parameter list which is not the default parameter list,
	       then the Get_Parameter_Attr() built-in is used.

	Scope: Globals preserve their value for the entire duration of
	       the Runform session, unless explicitly Erased. They are
	       visible to all forms which get called during the
	       session.  Any modificaton made in a called form to a
	       global variable is visible to any calling form and all
	       subsequent forms in the session.

	       Parameters are only visible to the form in which they
	       are declared, unless they are passed as part of a
	       parameter list, in which case they supply incoming
	       values for the form-level parameters declared for the
	       called form. The value of the parameter in the callin
	       form is thus visible to the called form in this
	       way. Any modification made in a called form to a
	       parameter is not visible to calling form.  The called
	       form gets "fed" a snapshot of the parameter values as
	       they existed at the moment of the Call_Form(), and
	       works with private copies of the values.

Documentation: Globals can be created anywhere in any trigger. Unless
	       a Forms developer is disciplined and uses some sort of
	       methodology, globals variables can be very hard to find
	       and document.

               Parameters exist as named object at the form level, can
	       have meaningful default values, and can be documented
	       with object comments like any other forms object.

--

Steve Muench         Email: smuench_at_oracle.com
Forms Development      CIS: 73404,676
Product Manager
Oracle Corporation