The server availability threshold specifies the lowest acceptable server availability index. Approximately once each minute, Domino® computes the server availability index and compares it to the server availability threshold that you set.

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If the availability index is less than or equal to the availability threshold, the server is marked as BUSY. When a server is marked as BUSY, requests to open databases are redirected to another server, if one is available. When the availability index becomes higher than the availability threshold again, the BUSY condition is withdrawn.

From the Domino Administrator

Procedure

1. Click the Configuration tab.

2. In the Task pane, expand Server, and then click Configurations.

3. Do one of the following:

• If a Configuration Settings document already exists for the server you want, select that document, and then click Edit Configuration.
• If a Configuration Settings document does not already exist for the server you want, click Add Configuration, and add the name of the server in the Group or Server name field on the Basics tab.

5. Click Set/Modify Parameters.

6. In the Item field, select or enter SERVER_AVAILABILITY_THRESHOLD.

7. In the Value field, enter the number you want for the server availability threshold.

The higher the number you enter, the less workload the server can carry before going into the BUSY state. Entering the number 100 automatically puts the server into the BUSY state, regardless of its actual availability. Entering the number 0 disables workload balancing for that server. The default value is 0.

9. Click Save & Close.

Using the availability threshold when you restart a server in a cluster

When you restart a server in a cluster, it is a good idea to make the server BUSY until all replication to the server is complete. This ensures that users access up-to-date information in the databases on the server. You can make a server BUSY by setting the availability threshold to 100. When replication is complete, make the server available to users.

Using the server availability threshold to control failover to specific servers

In some cases, you may want to limit failover to a server. For example, if you set up a cluster over a WAN and one of the cluster servers is more distant than the other servers, you may want to limit failover to the distant server. You can limit failover to this server by setting its availability threshold very high.

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For example, if you have three servers -- one in Boston, one in New York, and one in Hong Kong -- the Boston server would fail over to the Hong Kong server if it is more available than the New York server. However, if you set the availability threshold on the Hong Kong server to 100, the other cluster servers will not fail over to the Hong Kong server unless no other available cluster server contains a replica of the requested database.

When you control failover in this manner, be sure that the other cluster servers (the servers in Boston and New York in the example) have enough resources to handle most of the failover in the cluster.

Related tasks
The server availability index
Choosing the server availability threshold

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