For every async operation happens in Dynamics CRM 2011, a record gets saved in Asyncoperationbase table. So there is a possibility to grow this table very fast. To control growing this table size and save disk space, need to make sure following settings are done in Workflows and Plugins.
Workflows: If you open your workflow definition and go to the Administration tab, you will find the “Workflow Job Retention” option, under this you will see option to check “Automatically delete completed workflow jobs (to save disk space)”, If you click on the checkbox, it means that every time this workflow job is executed AND if it succeeds, the system job will be deleted. Selecting that option is perfect for processes that you don’t need to audit and you just need the logic to execute. However, if you need to keep a history of which workflows have executed on which records you should not select this option to delete the workflow job on completion (Note that this option is disabled by default).
Plugins: The similar option is also available for asynchronous plugin steps as well. When any asynchronous operation completes, a System Job entity is created to record the completion status. You can view these system jobs in the Web application by selecting Settings, and then click System Job. Check this option if you want plug-in related system jobs automatically deleted when the status is successful. (Note that this option is disabled by default for all asynchronous plugin steps).
In case If your AsyncOperationBase table becomes too large in Microsoft Dynamics CRM, you can follow Microsoft KB article to reduce the size.