The Oracle 10g Scheduler, Part 2: Implementation - Page 2
September 28, 2004
Viewing Scheduler Information
One of my pet peeves about DBMS_JOB is that only two views are provided to view the entire state of all scheduled tasks for the database. DBA_JOBS shows the current and future state of all scheduled tasks, and DBA_JOBS_RUNNING shows which tasks are running right now. Moreover, while DBA_JOBS can be queried to tell when a scheduled task last ran, it provides no information about how many times the task ran in the past, how many times it may have failed, and much more importantly why it failed.
Happily, the new Scheduler has rectified this by providing a plethora of views about its current and future state. I've assembled some queries that I have found useful in determining what Scheduler objects exist, what tasks have been scheduled, and the success or failure of each scheduled task activity after it has been run.
Scheduler Components. First, remember that all Scheduler components are actual database objects. The query in Listing 2.1 will show what jobs, programs, and schedules currently exist within the database:
Scheduler Objects: Object Owner Type Name Created On Status -------- ------------ -------------------- -------------------- -------SYS JOB GATHER_STATS_JOB 09/15/2004 20:47:25 VALID SYS JOB HR_FRESHENSCHEMA 09/21/2004 17:46:29 VALID SYS JOB PURGE_LOG 09/15/2004 20:26:09 VALID SYS JOB SH_FRESHENSCHEMA 09/21/2004 17:48:02 VALID SYS JOB SLSMGR_FRESHENSCHEMA 09/23/2004 19:13:13 VALID SYS JOB CLASS AUTO_TASKS_JOB_CLASS 09/15/2004 20:47:25 VALID SYS JOB CLASS DEFAULT_JOB_CLASS 09/15/2004 20:26:09 VALID SYS PROGRAM FRESHENALLSCHEMAS 09/23/2004 18:54:50 VALID SYS PROGRAM FRESHENSCHEMA 09/23/2004 18:57:57 VALID SYS PROGRAM GATHER_STATS_PROG 09/15/2004 20:47:22 VALID SYS PROGRAM PURGE_LOG_PROG 09/15/2004 20:26:09 VALID SYS SCHEDULE DAILY_PURGE_SCHEDULE 09/15/2004 20:26:09 VALID SYS SCHEDULE FRESHENSCHEMAS 09/19/2004 17:13:18 VALID SYS WINDOW WEEKEND_WINDOW 09/15/2004 20:47:22 VALID SYS WINDOW WEEKNIGHT_WINDOW 09/15/2004 20:47:18 VALID 15 rows selected.
Schedule Objects. The view DBA_SCHEDULER_SCHEDULES provides me with information about the schedules that are in effect in the database, as returned by the query in Listing 2.2.
Program Objects. View DBA_SCHEDULER_PROGRAMS shows all program objects and their attributes, while view DBA_SCHEDULER_PROGRAM_ARGS shows all program arguments for programs that have them. Listing 2.3 displays two sample queries against these two views.
Job Objects. Likewise, view DBA_SCHEDULER_JOBS shows all job objects and their attributes, while view DBA_SCHEDULER_JOB_ARGS shows the arguments that have been provided for each job that requires arguments. Listing 2.4 contains three queries for probing this information.
Scheduled Tasks Status and History. Three views track the status of all scheduled task activity for the database, including detailed history of each scheduled task's successful (or unsuccessful!) execution. This is a welcome addition to any DBA's tool belt for solving problems with scheduled tasks that may have failed unexpectedly. Listing 2.5 shows several +sample queries for gathering information on scheduled task execution, history, and current status.
View DBA_SCHEDULER_JOB_LOG shows a high-level summary of all job activity; its ADDITIONAL_INFO column is a CLOB that contains detailed information about the last run of the scheduled task.
View DBA_SCHEDULER_JOB_RUN_DETAILS shows an even greater level of detail about scheduled task run history; its ADDITIONAL_INFO column shows a brief description of what went wrong when a scheduled task has failed during execution.
Finally, view DBA_SCHEDULER_RUNNING_JOBS provides a method to look at a scheduled task while it is executing; this view replaces the old DBA_JOBS_RUNNING view.
Transitioning from DBMS_JOB to DBMS_SCHEDULER
To make the transition from using DBMS_JOB to DBMS_SCHEDULER, I suggest the following steps:
BEGIN DBMS_JOB.REMOVE(<job>, TRUE); ... COMMIT; END; /
As these examples have shown, Oracle 10g's new Scheduler offers a whole new range of flexibility when scheduling tasks. In my next article, I will delve into the details of scheduling tasks at non-standard date and time intervals. I will also explore some of the advanced features of the new Scheduler, including the ability to manage resource conflicts between scheduled tasks with Scheduler windows and job classes.
References and Additional Reading
While there is no substitute for direct experience, reading the manual is not a bad idea, either. I have drawn upon the following Oracle 10g documentation for the deeper technical details of this article:
B10802-01 Oracle 10g PL/SQL Packages and Types Reference
B10739-01 Oracle 10g Concepts, Chapters 25-28