This indicates that a general error occurred when Moodle tried to write to the database. If you turn on Debugging you will get more detailed information about what the problem is.
If you're using a MySQL database for your Moodle installation, this error can be caused by the server's
max_allowed_packet size being configured incorrectly. Increasing this value may resolve the issue.
dmlwriteexception error when restoring a course
If you obtain a dmlwriteexception error when restoring a course, it is recommended that InnoDB tables are converted to the Barracuda file format. See the section 'Converting InnoDB tables to Barracuda' in Administration via command line for details of why this is recommended plus information on a tool for converting tables.