Answer / shivaindu

When you use a Collection (Records, VARRAY etc having
records of data) as a Return type (OUT or IN OUT parameter)
as we know, it will be passed by value only. That means the
entire data will be copied to the formal parameter location,
which leads to lot of CPU and memory consumption.

Here comes the usage of NOCOPY parameter. Provide NOCOPY
after the OUT/IN OUT parameter, which instructs the PL/SQL
Engine to avoid using the pass by value method. So, the
Engine uses pass by reference instead. This helps reducing a
lot of CPU usage as well as memory consumption.
Eg: Just an example how to put the NOCOPY parameter.

PROCEDURE PRC_NOCOPY_EXAMPLE
(
P_EMPNO IN
NUMBER,
P_ENAME IN
VARCHAR2(50),
P_SAL OUT NOCOPY
RECORD_SAL --PL/SQL Record
);
REC_SAL RECORD_SAL;

Now if you call the Procedure PRC_NOCOPY_EXAMPLE, the
parameter P_SAL would only use Pass by reference method.
Disadvantage:
However, you need to be extremely careful while
using this method in coding for high priority data
transactions. When you pass parameters to a procedure by
reference, any change that happens on the passed Parameters
gets updated in the same memory location as the Actual
parameter. So when an exception occurs in a
procedure/function, these changes are not Rolled back . To
be precise, the PL/SQL engine cannot rollback these
parameter changes. So, if the actual values get changed,
then it may result in incorrect results.
Thus, to conclude, it is up to a Developer to take a
trade-off between using or not using the NOCOPY parameter.
NOCOPY could provide better performance by reducing Memory
and CPU cost, but at the same time, could result in
incorrect results too.

Answer / suresh somayajula

OUT and IN OUT Parameters which will avoid copy overhead.so we will use NOCOPY.

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