The action is meaningful only when you use a procedure with IN OUT parameters (a structure type) in context of object Event. It is unimportant for the RPC procedures.
When CALL action is executed, the action PRAGMA "ENABLE_INOUT_BY_REF" ensures that the real parameter, which inputs to the procedure via its formal parameter, will not be copied to the formal parameter of the procedure. It means that the formal parameter represents a reference to the real parameter.
Basically, CALL action creates a copy of the real parameter and uses it as the formal parameter. It causes:
A procedure call copies the procedure values uselessly (it is slower).
The formal parameter is "separated" from the real parameter.
PRAGMA "ENABLE_INOUT_BY_REF" ensures the formal parameter is "a reference" to the real parameter and the value is not copied. The procedure call is faster.
Example
PROCEDURE Proc1(RECORD (SD.Data) _data)
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_data[1]^Col :=2
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END Proc1
BEGIN
PRAGMA "ENABLE_INOUT_BY_REF"
RECORD (SD.Data) _rec
REDIM _rec [2]
_rec[1]^Col :=0
CALL Proc1(_rec)
END
An application of PRAGMA "ENABLE_INOUT_BY_REF" action: The formal parameter _data is the real parameter _rec. When you write _data[1]^Col := 2, the value "2" is assigned to the real parameter _rec[1]^Col.
An application of CALL action (PRAGMA "ENABLE_INOUT_BY_REF" action is not used): The formal parameter _data is an absolute copy of the real parameter _rec. When you write _data[1]^Col := 2, the value "2" is assigned to the formal parameter _data. After CALL proc1(_rec) is executed, the formal parameter _data will be copied to the real parameter _rec.
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