another one of those errors that can appear in your ULS logs which can easily be solved. This error also logs events in the Application eventlog with ID 6398 and 5586.
I found the solution to this issue on the SharePoint forum here
This happens when you have the Usage and Health Data Collection Service Application installed. This service application creates a database just for logging. Apparently the Search Service was trying to make entries in that database and couldn’t.
The solution to this issue is to enable the Usage Data Collection, which is not enabled by default when you create the Usage and Health Data Collection Service Application .
To enable the Usage Data Collection navigate to Central Admin\Application Management\Service Applications\Manage service applications. Once there highlight the WSS_UsageApplication (or whatever name you gave the service application)and select manage from the ribbon. Under Usage Data Collection check the box. Under Health Data Collection check the Enable health data collection box. Hit OK and the errors will be gone.