Question
Answer and Explanation
Automating or scheduling custom PL/SQL procedures in Oracle can be accomplished through several methods. Here are the most common approaches:
1. Oracle Scheduler:
- The Oracle Scheduler is the most robust and recommended method for scheduling jobs in Oracle. It provides advanced features such as job chains, resource management, and error handling.
- How to use it:
a. Create a PL/SQL procedure that encapsulates the logic you want to execute. For example:
CREATE OR REPLACE PROCEDURE MY_CUSTOM_PROCEDURE AS
BEGIN
-- Your PL/SQL logic here
DBMS_OUTPUT.PUT_LINE('Custom procedure executed');
END;
/
b. Create a job using `DBMS_SCHEDULER`:
BEGIN
DBMS_SCHEDULER.CREATE_JOB(
job_name => 'MY_SCHEDULED_JOB',
job_type => 'STORED_PROCEDURE',
job_action => 'MY_CUSTOM_PROCEDURE',
start_date => SYSTIMESTAMP, -- when to start
repeat_interval => 'FREQ=MINUTELY;INTERVAL=5', -- every 5 minutes
enabled => TRUE);
END;
/
- This example creates a job named 'MY_SCHEDULED_JOB' that executes 'MY_CUSTOM_PROCEDURE' every 5 minutes starting immediately.
c. To check the scheduled jobs, use the following query:
SELECT job_name, enabled, state, last_start_date, next_run_date FROM user_scheduler_jobs;
2. DBMS_JOB (Legacy):
- `DBMS_JOB` is a legacy package used for job scheduling. While still functional, `DBMS_SCHEDULER` is recommended for new implementations.
- How to use it:
DECLARE
jobno NUMBER;
BEGIN
DBMS_JOB.SUBMIT(job => jobno,
what => 'MY_CUSTOM_PROCEDURE;',
next_date => SYSDATE,
interval => 'SYSDATE + 1/24'); -- Execute hourly
DBMS_OUTPUT.PUT_LINE('Job submitted: ' || jobno);
COMMIT;
END;
/
- This example submits a job that will execute 'MY_CUSTOM_PROCEDURE' hourly.
3. Operating System Scheduling (e.g., Cron on Linux/Unix, Task Scheduler on Windows):
- You can schedule scripts at the OS level to connect to your database and execute the required PL/SQL procedure.
- How to use it:
a. Create a shell or batch script that uses SQLPlus to connect to the database and execute the procedure. For example, on Linux/Unix:
sqlplus user/password@database << EOF
SET SERVEROUTPUT ON
EXEC MY_CUSTOM_PROCEDURE;
EXIT;
EOF
b. Use `cron` (on Linux/Unix) or Task Scheduler (on Windows) to schedule this script to run at the desired times.
4. Oracle Streams or Advanced Queuing (AQ):
- These technologies can be used to trigger PL/SQL procedures based on specific data events, not as classic time-based scheduling, but as event-driven execution.
Key considerations:
- Error Handling: Ensure that your scheduled procedures include robust error handling and logging.
- Permissions: The user running the scheduled job must have the necessary privileges to execute the procedure and access related objects.
- Resource Usage: Monitor resource consumption by your jobs to avoid performance issues.
- Maintainability: Document your scheduled jobs for better maintenance and troubleshooting.
In summary, while several options exist, the Oracle Scheduler is the most modern and feature-rich option for automating PL/SQL procedures. Choose the approach that best suits your specific needs and technical environment, ensuring you include adequate error handling and monitoring.