SQL Server NETWORKIO Wait Type

The NETWORKIO wait type occurs because the SQL Server is waiting for data to be sent to or from the server and the network is not quick enough to transfer the data.

Basic tuning for the NETWORKIO wait type

To remedy the NETWORKIO wait type either less data needs to be returned to the client or the network between the client and the SQL Server needs to be faster.

If you run queries within SQL Server Management Studio from a remote site and there are large record sets being returned, you are seeing the NETWORKIO wait type.

Unfortunately there is no solution for this wait type in the SQL Server instance except to increase the speed (or total bandwidth) of the network between the user and the SQL Server or to decrease the size of the record set being returned by the client.

Advanced tuning for the NETWORKIO wait type

If either of these solutions are not an option, more creative actions may help. Here are som examples:

1. Peer to peer mirroring would allow you to move a copy of the data closer to the users while keeping the original server in the original location. When the users connect to the server that is closer to them the NETWORKIO wait type should resolve. This may not be the case if the local network is too slow.
2. Upgrading to 1 GB network links may help solve the problem if the SQL Server is older and using 100 Meg network links.
3. You can assess network ports between network switches or the backplane on the network switch that both computers are connected to. The NETWORKIO wait type can be caused if any of these network devices are out of capacity.
4. Network switch port errors should also be reviewed. The SQL Server NETWORKIO errors can occur if there are errors on the switch port that could cause performance problems due to the errors and packets needing to be retried.
5. Finally, if the server (or workstation) NIC has been configured for auto-sync when connected to the switch port problems could arise. If the switch and the NIC don’t negotiate the correct speed, they may get stuck at the slowest possible speed, typically 10 Megabit half duplex. At this speed the performance of the SQL Server will be extremely slow and possibly trigger the SQL Server NETWORKIO wait type.