This content originally appeared on DEV Community and was authored by Pranav Bakare
PRAGMA SERIALLY_REUSABLE in PL/SQL —
In PL/SQL, we often use packages to hold variables, cursors, and procedures. Normally, package variables maintain their state throughout a user’s session, meaning that once you set a value, it stays until you disconnect. But sometimes, this behavior can waste memory when thousands of sessions are open, and each is holding unnecessary package state. To address this, Oracle provides PRAGMA SERIALLY_REUSABLE, which tells the compiler that the package state should only exist for the duration of a single call. After the call ends, Oracle automatically erases the package’s memory, ensuring efficient memory usage.
📌 The Whiteboard Analogy
- Think of PRAGMA SERIALLY_REUSABLE as a whiteboard in a classroom.
- During a lecture (a PL/SQL block execution), the teacher writes notes (package variables).
- Students use this information while the lecture is ongoing.
- Once the lecture ends (execution finishes), the board is wiped clean (memory released).
- When the next lecture begins (a new call), the board is blank again, ready for fresh notes.
- This analogy perfectly explains how Oracle treats packages marked with SERIALLY_REUSABLE: temporary storage, automatically reset after each call.
📌 Practical Example
Let’s create a package that demonstrates this behavior:
-- Package with PRAGMA SERIALLY_REUSABLE
CREATE OR REPLACE PACKAGE temp_pkg
PRAGMA SERIALLY_REUSABLE AS
g_message VARCHAR2(100) := 'Initial';
PROCEDURE set_message(p_msg VARCHAR2);
PROCEDURE show_message;
END temp_pkg;
/
CREATE OR REPLACE PACKAGE BODY temp_pkg
PRAGMA SERIALLY_REUSABLE AS
PROCEDURE set_message(p_msg VARCHAR2) IS
BEGIN
g_message := p_msg;
END;
PROCEDURE show_message IS
BEGIN
DBMS_OUTPUT.PUT_LINE('Message = ' || g_message);
END;
END temp_pkg;
/
📌 Execution and Output
BEGIN
temp_pkg.set_message('Hello');
temp_pkg.show_message; -- Output: Message = Hello
END;
/
BEGIN
temp_pkg.show_message; -- Output: Message = Initial (state reset, like a cleaned whiteboard)
END;
/
🔎 Explanation:
- In the first block, we updated g_message to “Hello,” and it printed correctly.
- But once the block ended, Oracle wiped the memory used by the package.
- In the next block, the variable returned to its default value (Initial), proving that the package does not persist its state across calls.
📌 When to Use
- When package variables are temporary and do not need to persist across calls.
- To reduce memory usage in systems with many users accessing packages.
- For short-lived values like counters, temporary logs, or small caches.
📌 Seven-Liner Summary
PRAGMA SERIALLY_REUSABLE is a PL/SQL compiler directive that makes package variables temporary instead of session-persistent.
It allocates memory only during a call and frees it immediately once the call ends.
This prevents memory bloat in large, multi-user systems where many sessions access the same package.
Unlike normal packages, state is not carried forward between different calls.
A perfect analogy is a classroom whiteboard that is erased after each lecture.
Each execution starts with a fresh package state, initialized with default values.
Thus, it is ideal for temporary, non-persistent tasks where maintaining state is unnecessary.
PRAGMA SERIALLY_REUSABLE in PL/SQL is a compiler directive that ensures the package memory is allocated only during a single program call and released as soon as the call ends. This has a significant impact on memory management because package variables, which normally persist for the entire user session, no longer occupy memory unnecessarily across multiple executions. Its ideal feature is that it prevents the accumulation of unused session state, making it very useful in systems with thousands of users where conserving memory is critical. Each new call to such a package begins with freshly initialized variables, ensuring that no previous state is carried forward. This makes it best suited for temporary operations where maintaining state across calls is neither required nor desirable.
For example, consider a package that maintains a message variable or a counter. If the package is defined as serially reusable, setting a message or incrementing the counter during one block execution will only hold for that call. The moment the block ends, Oracle releases the memory and the variables revert to their default values. When the next block executes, the package begins afresh as though nothing was stored before, ensuring no state leakage from the past. This is much like a classroom whiteboard: notes written during the lecture are useful while it lasts, but once the lecture ends, the board is erased, ready for the next session. In the same way, PRAGMA SERIALLY_REUSABLE guarantees that each call starts with a clean state, optimizing memory usage while maintaining clarity and consistency of execution.
— — — — —
PRAGMA SERIALLY_REUSABLE
PRAGMA SERIALLY_REUSABLE in PL/SQL is a compiler directive that ensures the package memory is allocated only during a single program call and released as soon as the call ends. This has a significant impact on memory management because package variables, which normally persist for the entire user session, no longer occupy memory unnecessarily across multiple executions. Its ideal feature is that it prevents the accumulation of unused session state, making it very useful in systems with thousands of users where conserving memory is critical. Each new call to such a package begins with freshly initialized variables, ensuring that no previous state is carried forward. This makes it best suited for temporary operations where maintaining state across calls is neither required nor desirable.
For example, consider a package that maintains a message variable or a counter. If the package is defined as serially reusable, setting a message or incrementing the counter during one block execution will only hold for that call. The moment the block ends, Oracle releases the memory and the variables revert to their default values. When the next block executes, the package begins afresh as though nothing was stored before, ensuring no state leakage from the past. This is much like a classroom whiteboard: notes written during the lecture are useful while it lasts, but once the lecture ends, the board is erased, ready for the next session. In the same way, PRAGMA SERIALLY_REUSABLE guarantees that each call starts with a clean state, optimizing memory usage while maintaining clarity and consistency of execution.
This content originally appeared on DEV Community and was authored by Pranav Bakare
Pranav Bakare | Sciencx (2025-08-26T17:16:37+00:00) PRAGMA SERIALLY_REUSABLE in PL/SQL. Retrieved from https://www.scien.cx/2025/08/26/pragma-serially_reusable-in-pl-sql/
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