Automated Maintenance Tasks

With Oracle Database 11g, the Automated Maintenance Tasks feature relies on the Resource Manager being enabled during the maintenance windows.

The resource plan associated with the window is automatically enabled when the window opens. 

The goal is to prevent maintenance work from consuming excessive amounts of system resources.Each maintenance window is associated with a resource plan that specifies how the resources will be allocated during the window duration.

In Oracle Database 11g, WEEKNIGHT_WINDOW and WEEKEND_WINDOW (defined in Oracle Database 10g) are replaced with daily maintenance windows. 

Automated Maintenance Task Priorities 

• The Automated Maintenance Tasks feature is implemented by Autotask Background Process (ABP). ABP functions as an intermediary between automated tasks and the Scheduler. 
• Its main purpose is to translate automated tasks into AUTOTASK jobs for execution by the Scheduler. 
• Just as important, ABP maintains a history of execution of all tasks. ABP stores its private repository in the SYSAUX tablespace; you view the repository through DBA_AUTOTASK_TASK. 
• ABP is started by MMON at the start of a maintenance window. There is only one ABP required for all instances. The MMON process monitors ABP and restarts it if necessary. 
• ABP assigns jobs to various Scheduler job classes. These job classes map the job to a consumer group based on priority.
• The Automatic Maintenance Tasks feature determines when—and in what order—tasks are performed. As a DBA, you can control the following:
• If the maintenance window turns out to be inadequate for the maintenance workload, adjust the duration and start time of the maintenance window.
• Control the resource plan that allocates resources to the automated maintenance tasks during each window.
• Enable or disable individual tasks in some or all maintenance windows.
• In a RAC environment, shift maintenance work to one or more instances by mapping maintenance work to a service. Enabling the service on a subset of instances shifts maintenance work to these instances.
• Enterprise Manager is the preferred way to control Automatic Maintenance Tasks. However, you can also use the DBMS_AUTO_TASK_ADMIN package.