You can run a Verify on your records and indexes while 4D Server is running without having to restart the database. Go into the 4D Server Administration Window and select the Maintenance tab. From there click the Verify Records and Indexes button.
While the verify is occurring clients will see a message such as this:
While this is up the client will not be able to manipulate data, as the data file is effectively in read-only mode.
The Maintenance tab of 4D Server is covered in detail here: