On start-up, a server that is a member of a cluster uses the com.sybase.jaguar.cluster.startup cluster property to determine whether it is “in sync” with other cluster members. Check or modify this property from the Advanced tab in the Cluster Properties window—see com.sybase.jaguar.cluster.startup. com.sybase.jaguar.cluster.startup can have these values:
check_primary (default value)
If any other cluster member (including the primary) is reachable and has a higher cluster version number, this server moves to Admin mode since it is not “in sync.”
If the primary is available and has the same cluster version number, this server joins the cluster and is ready to accept client connections.
If the primary is available and has a different cluster version number, this server moves to Admin mode since it is not “in sync.”
If none of the above conditions are met, the server waits briefly, then returns to step a.
check_servers
If any other cluster member (including the primary) is reachable and has a higher cluster version number, this server moves to Admin mode since it is not “in sync.”
Let M be the number of cluster members (including the primary), and let N equal M/2 (integer division). If at least N other servers are available and have the same cluster version number, this server joins the cluster and is ready to accept client connections.
If none of the above conditions are met, the server waits briefly then returns to step a.
The check_servers option allows a server to join a cluster even if the primary is not available. This prevents a single point of failure if the primary server becomes unavailable.
disable_check – no checking is performed. For a cluster with only two servers (including the primary), use this option, and manually verify that the secondary server is “in sync.” For a cluster with three or more servers, Sybase discourages the use of this option, since it can result in “out-of-sync” cluster members running together.
A server in Admin mode can be put into Ready mode as described in “Switching to Ready mode”. If a server is in Admin mode due to a cluster version number mismatch, then using Set Ready is the manual equivalent of disable_check, so using Set Ready in this case is also discouraged as it may result in “out-of-sync” cluster members running together. Sybase recommends that you synchronize the cluster instead. See “Synchronizing a cluster from EAServer Manager” for more information.
| Copyright © 2003. Sybase Inc. All rights reserved. |
|
|
