Setting a community-level limit on sessions in Sametime Gateway

You can limit the maximum number of sessions allowed on a server by each community in IBM® Sametime® Gateway, which helps prevent out-of-memory errors. The total sessions for individual communities on a particular server contribute to that server's "global" total number of sessions.

Before you begin

If you have more than one external community, there are a number of factors to consider when deciding on community-level maximum session limits. The following table shows different strategies for choosing community limits:
Table 1. Scenarios for setting maximum number of sessions for external communities
Scenario Settings Comments
Scenario 1

global max=10

community A max=5

community B max=5

Because G=10, there cannot be more than 10 sessions in a community.

Pros: An overloaded community (A=5) will not interfere with community B reaching its own specified maximum (B=5),

The server resources are not fully utilized: even if community A uses less than 5 sessions, community B cannot use more than its own limit of 5 sessions.

Scenario 2

global max=10

community A max=10

community B max=10

Because G=10, there cannot be more than 10 sessions in a community.

Pros: The server resources are fully used; if community A uses less then 5 sessions then community B could use more than 5 sessions.

Cons: Communities are not insulated and protected from each other. If community A has 8 sessions, then community B can only have 2 sessions (since G=10).

Attention: In a cluster, the maximum number of sessions is applied to each node, so the true maximum is the number of nodes multiplied by the maximum sessions value; for example, if your cluster has two nodes and your maximum sessions is set to 5000, then your cluster actually supports a maximum of 2 * 5000 = 10,000 sessions.

About this task

When a user subscribes to be notified of another user's status changes, a presence session object is created. When two users start a new chat, an instance messaging session object is created. These session objects take up considerable space in memory. To avoid a scenario in which a very high level of user activity might cause an out-of-memory error to occur, set the maximum session property to a predefined limit that you know is supported. In the event of these limits being reached, the server does not create any new sessions, but does continue to serve existing sessions.

There are two configuration levels regarding the maximum sessions limit in Sametime Gateway Server: global limits and community limits. For information about global limits, see the topic Setting a global limit on sessions.

The procedure that follows sets community-level limits for the maximum number of sessions allowed at one time on a particular server.

Expected state:
  • Single server: theSametime Gateway Server is started.
  • Cluster: the deployment manager is started, and the node agent and the Sametime Gateway Server are started on at least one node.
Note: If you set a community's session limits to a value higher than the overall global limit, the global limit is enforced.

Procedure

  1. In the Integrated Solutions Console, click Sametime Gateway > Communities.
  2. In the "Communities" table, select a community for which you want add or change session limits.
  3. Under the Additional Properties section, click Assign local users and capabilities.
  4. Set the maximum sessions for instant messaging by typing an integer.

    The recommended value is the matching global value divided by the number of external communities, though you may choose a different limits strategy.

  5. Set the maximum sessions for presence by typing an integer.

    The recommended value is the matching global value divided by the number of external communities, though you may choose a different limits strategy.

  6. Click Apply.
  7. Restart the Sametime Gateway Server; if you have a cluster of Sametime Gateway Servers, restart the cluster.

What to do next

Note: If you set either (or both) of the community's session limits to a value higher than the overall global limit, the global limit will still be enforced.