The Engineer's Edition Network Performance Monitor uses a Microsoft Access database. Access databases have an inherent file size limit of 2GB. Once your database reaches this size, the Network Perforance Monitor will no longer be able to store statistics.
If you are monitoring a large network or storing data over an extended period of time you should consider using the Orion Network Performance Monitor which uses a Microsoft SQL Server database.
To continue using the Engineer's Edition Network Performance Monitor, you will want to shrink the database periodically.
This error occurs due to database nearing its 2 Gigbyte size limit.
C:\Program Files (x86)\SolarWinds\Toolset\Database-Maint.exe
3. Select Compact and Repair"and click Run Job.
4. Select Network Performance Monitor - Nightly Maintenance and click Run Job.
5. Open Network Performance Monitor.
5. Once the repair has completed, close Access.
6. Open Network Performance Monitor.