Data exchange via local SQL DB table

[JordanCClark]

Normally, I'd say the buffer cache should be sufficient for this operation. However, you'll need to balance SQL Server memory requirements to Ignition's.

System Slowing down over a period

+1 on what Phil said. The database should be on a separate host. In the meantime, check the memory allocation to SQL server. and set it to something reasonable. By default, it will use all the memory it can. This article can give some handy calculations.