Particularly in environments with shared resources contention may occur. Important databases need to be prioritized while less important ones should be suspended.
For this purpose, you can use the "suspend" command:
alter system suspend;
Alert log:
Mon Oct 05 10:14:49 2015 Suspending database after alter system suspend command
The database_status field in v$instance will reflect the new state of the database:
SQL> select database_status from v$instance; DATABASE_STATUS ----------------- SUSPENDED
When you are ready to resume database activity, issue the following command:
alter system resume;
More info: Oracle Documentation
