Use serially reusable packages - performance of application, PL-SQL Programming

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Use Serially Reusable Packages

To help you to manage the use of memory, the PL/SQL gives the pragma SERIALLY_ REUSABLE that mark some packages as serially reusable. So mark a package if its state is required only for the duration of one call to the server (for illustration, an OCI call to the server or a server-to-server RPC).

The global memory for these packages is pooled in the System Global Area (SGA), not allocated to the individual users in the User Global Area (UGA). In that way, the package work region can be reused. If the call to the server ends, the memory is return to the pool. Each time the package is reused, the public variables are initialized to its default values or to NULL.

The maximum number of work regions required for a package is the number of concurrent users of that package that is usually much smaller than the number of logged-on users. The bigger use of SGA memory is more than offset by the reduced use of UGA memory. The Oracle ages-out work areas are also not in use if it requires reclaiming the SGA memory.

For packages without a body, you code the pragma in the package specification using the

Syntax as shown:

PRAGMA SERIALLY_REUSABLE;

For packages with a body, you should code the pragma in the specification and body. You cannot only code the pragma in the body. The illustration below shows how a public variable in a serially reusable package behaves across the call boundaries:

CREATE OR REPLACE PACKAGE sr_pkg IS

PRAGMA SERIALLY_REUSABLE;

num NUMBER := 0;

PROCEDURE init_pkg_state(n NUMBER);

PROCEDURE print_pkg_state;

END sr_pkg;

/

CREATE OR REPLACE PACKAGE BODY sr_pkg IS

PRAGMA SERIALLY_REUSABLE;

/* Initialize package state. */

PROCEDURE init_pkg_state (n NUMBER) IS

BEGIN

sr_pkg.num := n;

END;

/* Print package state. */

PROCEDURE print_pkg_state IS

BEGIN

DBMS_OUTPUT.PUT_LINE('Num is: ' || sr_pkg.num);

END;

END sr_pkg;

/

BEGIN

/* Initialize package state. */

sr_pkg.init_pkg_state(4);

/* On same server call, print package state. */

sr_pkg.print_pkg_state; -- prints 4

END;

/

-- subsequent server call

BEGIN

-- package's public variable will initialized to its

-- default value automatically

sr_pkg.print_pkg_state; -- prints 0

END;


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