Applies To:
  • CitectSCADA
  • CitectHMI
Summary:
While using [LAN]Netbios=1 you may get the following error "Error 0x11 - Local session table full".

This Knowledge Base article describes how to calculate whether NetBios will be able to handle the number of sessions in a Citect installation, and suggests ways of increasing the number of sessions.

 

Solution:
When using NetBios, each server is limited to 255 sessions per (network card * no. of protocols). A Server uses 1 session per service for each client attached. So if a computer is an Alarms, Trends, Reports, and I/O Server each client will use 4 sessions. The most clients that it will be able to service is 255 / 4 = 63. Also you should also allow 50% extra sessions for during a redundant changeover when you get an extra peak loading. Therefore the most clients that a single server running Alarms, Trends, Reports, and I/O can safely handle is 42. If you are getting the "Local session table full" error while using NetBios, there are several things to try:

* Increase the [LAN]Sessions parameter (maximum setting value is 1024), however NetBios will only support 255.

* Distribute the various servers (I/O, Alarm, Trends, Reports) over several machines. If you run three servers on one machine and one on another you can safely support 63 clients. If split the 4 servers evenly over two machines with two servers on each machine you can safely support 84 clients, and if you have a separate machine for each server you can safely support 168 clients while still allowing for an additional 50% peak loading.

* Use TCP/IP. TCP/IP does not have the 255 session limit that NetBios does. To use TCP/IP make the following changes to 'citect.ini' [LAN]Netbios=0, [LAN]Tcpip=1. It is recommended trying Netbios first as it is more stable with Citect than TCP/IP.

 
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