PL/SQL procedure successfully completed.

This example instructs Oracle to automatically purge all records that are over 60 days old.

By default, this procedure sets the history retention period for both Scheduler window logs and Scheduler job logs. To set only one, you may include the WHICH_LOG parameter to specify either WINDOW_LOG or JOB_LOG.

Creating and Using Job Classes

A job class is a container object for the logical grouping of jobs into a larger unit. Classifying jobs in this manner offers several advantages:

NNFrom an administrative perspective, it is easier to manage a small number of job groups than to manage a large number of individual jobs. Certain job characteristics can be assigned at the group level and will be inherited by all jobs within the group. Certain administrative procedures will also operate at the group level, making administrative functions easier.

NNJob classes can be assigned to a resource consumer group. This allows you to control resource allocation for all jobs within the group.

NNJobs can be prioritized within the job class. This gives you more control over which jobs should take precedence in case of a conflict. For example, if a conflict occurs, the JOB_ PRIORITY attribute of each job will be evaluated. A job with a value of HIGH takes priority over a job with a value of LOW.

All jobs must belong to exactly one job class. Any job not explicitly assigned to a job class will belong to the DEFAULT_JOB_CLASS class and will inherit the characteristics of that job class. In the following sections, you will learn to create and administer job classes.

Job Class Parameters

Job classes have a specific set of attributes that you can set to define the characteristics of the class. These attributes will be inherited by all jobs assigned to the job class, thereby saving you the work of setting them individually on each job. The available attribute parameters are described here:

JOB_CLASS_NAME  The JOB_CLASS_NAME parameter uniquely identifies the job class in the SYS schema. The name has to be unique in the SYS schema.

RESOURCE_CONSUMER_GROUP  The RESOURCE_CONSUMER_GROUP parameter associates the job group with a specific consumer group. All jobs assigned to the job group will automatically be governed by this consumer group.

SERVICE  The SERVICE parameter specifies the service to which the job class belongs. This means that, in a RAC environment, the jobs in this class will have affinity to the particular service specified. Therefore, they will run only on those database instances that are assigned to the specific service. If this attribute is not set, the default service will be used, meaning that the jobs have no service affinity and can be run by any instance within the cluster. If the SERVICE parameter is specified, the RESOURCE_CONSUMER_GROUP attribute cannot be set. They are mutually exclusive.

LOGGING_LEVEL  The Oracle Scheduler can optionally maintain job logs of all job activities. Job logging is determined by the setting of the LOGGING_LEVEL attribute of the job class. The LOGGING_LEVEL parameter specifies how much job information is logged. There are four valid settings for this attribute:

DBMS_SCHEDULER.LOGGING_OFF  No logging will be performed for any jobs in this class.

DBMS_SCHEDULER.LOGGING_RUNS  Detailed information will be written for all runs of each job in the class.

DBMS_SCHEDULER.LOGGING_FULL  Detailed information will be written for all runs of each job in the class, and every operation performed on any job in the class (create, enable, drop, and so on) will be logged.

DBMS_SCHEDULER.LOGGING_FAILED_RUNS  Logs only jobs that failed and the reason for failure. If the job class has a higher logging level the higher level takes precedence.

Note that the valid values for this parameter are all constants defined within the DBMS_ SCHEDULER package. Therefore, they must be referenced exactly as shown, with no quotes around them.

LOG_HISTORY  The LOG_HISTORY parameter determines the number of days logged information should be retained. The default value is 30 days. Valid values are 1 to 999. When records have exceeded this limit, the Scheduler will automatically purge them.

COMMENTS  The COMMENTS parameter specifies an optional comment about the job class.

Creating Job Classes

Job classes can be created through the DBMS_SCHEDULER.CREATE_JOB_CLASS procedure, as shown in the following example:

SQL> begin

2dbms_scheduler.create_job_class(

3 job_class_name => ‘LOW_PRIORITY_CLASS’, 4 resource_consumer_group => ‘LOW_GROUP’,

When working with a job class, you can define a resource consumer group and take advantage of the Database Resource Manager capabilities, as described earlier in this chapter. You can also prioritize jobs within a job class.

Prioritizing Jobs within a Job Class

Within a job class, you can assign priority values from 1 to 5 to individual jobs so that if more than one job within the same class starts at the same time, the job with the highest priority will take precedence over the others. If two jobs have the same priority, the one that had the earlier start date gets the higher priority. Priority rules apply only when comparing jobs within the same class. The default priority for a job is 3; 1 is the highest, and 5 is the lowest.

To change a job priority, use the SET_ATTRIBUTE procedure. For example, here’s how to raise the priority of the LNE_JOB1 job to priority 1:

BEGIN DBMS_SCHEDULER.SET_ATTRIBUTE (

name => ‘lne_job1’, attribute => ‘job_priority’, value => 1);

END;

/

The job_priority attribute is set by default to 3 when you create the job; use the SET_ATTRIBUTE procedure to change the job priority.

Using Scheduler Views

Oracle offers a wide variety of views to access information regarding the Scheduler and its associated objects. These views allow you to see information about currently running jobs and past runs of jobs. Table 12.5 describes the available Scheduler views.

Ta b l e 12 . 5   ​  Scheduler​ Views Available