Automatic import from KB #3466
"DS not found" error is thrown for domain service related tasks, for example: "Disable domain service (ds_id=<ds_id>, hd_id=<hd_id>) on host '<hostname>' (host_id=<host_id>)" can fail with this error.
This error is caused by the fact, that some operations were scheduled for a nonexistent domain service. Such kind of inconsistencies may appear due to manual database intervention or changing POA tasks processing order - canceling and rescheduling related tasks.
As these tasks are scheduled for nonexistent domain service, they can be canceled.