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Chapter 13 Managing Distributed Data Synchronization
This chapter describes how to group iPlanet Application Servers into data synchronization clusters.The following subjects are described in this chapter:
About Distributed Data Synchronization
How Failover Keeps Data Accessible
About Distributed Data Synchronization
Distributed data synchronization maintains the integrity of shared state and session information across multiple iPlanet Application Server (iAS) machines. This is crucial for partitioned and distributed applications that are hosted on multiple iAS machines.In most enterprises, several iAS machines support one or more distributed applications. For such distributed applications to run successfully, each server must have access to the pertinent information for that application, such as state and session information.
Support for this distribution of information is provided through a system-level distributed data synchronization service that is built into iAS.
How Failover Keeps Data Accessible
The distributed data synchronizer is a system-level service that controls how distributed data, such as application session information, is maintained and made accessible across multiple iPlanet Application Server (iAS) machines.Each iAS machine is made up of the following four "engines:"
Administrative Server (KAS) - An Administrative Server brings up and monitors the other engines and makes sure that any engines that fail are brought up again.
Executive Server (KXS) - Only an Executive Server can be the primary synchronization engine (the synchronizer) for an iAS cluster.
Zero or more Java Servers (KJS)
- In a cluster of iAS machines, one of the Executive Servers maintains the distributed (synchronized) information and sets up server roles for all the other servers participating in the cluster. All engines in a cluster know how to access this primary engine and the information that is on this primary engine.
Zero or more C++ Servers (KCS)
- If the Java or C++ engine on an iPlanet Application Server fails, the Administrative Server simply restarts the KJS or KCS. However, if the Executive Server fails, the Administrative Server performs the following actions:
What Is a Cluster?
A cluster is a group of iPlanet Application Server (iAS) machines that synchronizes data. Servers in a cluster are connected by the same network.Data that is shared by all the iAS machines in a cluster is stored in iPlanet Directory Server. Each iAS machine in your cluster should share one Directory Server; if the iAS machines in your cluster do not share a single Directory Server, cluster settings must be copied from one Directory Server to another so each server has access to identical cluster information. This defeats the purpose of Directory Server, which is designed to simplify information storage by storing the data shared by servers in your enterprise in a central location.
Setting Up Data Synchronization
To set up data synchronization between servers, you must first decide what general role each server performs in the cluster. Then you can edit each cluster entry to set up the server roles and to register the cluster with the synchronizer service. Finally, start each iAS in the order that is determined by server roles.
Synchronization Server Roles
Each server that participates in data synchronization can be set up to fill any one of the roles described in the following table.
How a Cluster Communicates
Servers in a cluster communicate using the GXCONN communication protocol. However, before the servers in a cluster can communicate with each other, each server has to know what cluster it belongs to. iAS becomes an active part of a cluster when you map its synchronizer to the cluster. This procedure is described in .When an application component requests "write" access to a distributed data source, the write occurs first on the Sync Primary. When the data changes on the Sync Primary, the Sync Primary immediately updates the Sync Backups.
Although you can define as many clusters as you like, the synchronizer for each iAS machine can be mapped to only one cluster at a time.
Information Flow Within a Cluster
Sync Backups, Sync Alternates, and Sync Locals communicate with the Sync Primary in a star configuration, as shown in the following illustration:
In this illustration, notice that all servers are communicating with the Sync Primary, although the Sync Backups communicate with it most closely. Also, notice that no Sync Local is assigned a priority number.
Note also that the illustration is an ideal representation of a cluster that has probably just started and has not experienced failover, in that the priority numbers correspond gracefully with the currently assigned roles.
Setting Up and Managing Clusters
Before you set up and begin managing clusters, review the following steps, which provide an overview of the general procedure. More specific procedures for setting up and managing clusters are described in subsequent sections.
Decide which servers will participate in a synchronization group (cluster), and which of those servers will be Sync Servers, eligible to act as the Sync Primary and as Sync Backups, and which will be Sync Locals.
Edit the kregedit keys under Clusters and ClusterName on one of the Sync Servers. Duplicate the ClusterName edits to the registries of all the other servers in the cluster (including the Sync Locals). You need not duplicate edits to the Clusters key since this information is stored in a centrally located Directory Server.
Create the kregedit keys that will contain synchronization information, if necessary.
Enter the name of the cluster in the ClusterName key.Edit the SyncServers kregedit key to contain identification information and the priority setting for each Sync Server in the cluster. Often, the larger and more powerful servers are chosen to be the highest-priority Sync Servers.
Set the MaxBackups kregedit key to the number of Sync Backups. Sync Backups are servers that duplicate the data on the Sync Primary.
Start the Sync Server that will be the Sync Primary. The server that you want to be the Sync Primary must always be the first server to be started in the cluster, and it becomes the Sync Primary simply because it started first.
- Make sure that the kregedit keys under ClusterName are identical on all servers in the cluster, including the Sync Locals. Each SyncServers kregedit key must list the same Sync Servers with the same priority numbers, or the cluster will not function properly.
After starting the Sync Primary, start the other servers (including the Sync Locals). Although the starting order is not mandated after the Sync Primary starts, it is a good practice to start the Sync Servers in priority order, and then to start the Sync Locals.
Start the servers that will become the Sync Backups, up to the value of MaxBackups. By default, the next servers listed in the SyncServer key that start, up to the value stored under the MaxBackups kregedit key, will become the Sync Backups.
After MaxBackups number of servers have started, remaining Sync Servers that start become Sync Alternates.
All servers not listed in the SyncServers kregedit key become Sync Locals. Sync Locals are part of the cluster simply because each is mapped to the cluster and the SyncServers kregedit key on each contains a list of all the Sync Servers in the cluster.
Determining Sync Server Priority
The specific procedure for setting priority is covered in and . The following section discusses general priority issues and gives a comprehensive example of cluster coordination.Priority is indicated by an integer value that is set in the SyncServers kregedit key. The lower the value, the higher the priority, so the server assigned a value of 0 has the highest possible priority. The highest acceptable value, and so the lowest priority value, is 65,535.
Priority values are used only to select between Sync Servers in the same status (either between a group of Sync Backups or between a group of Sync Alternates). Only the order in which instances of iAS are started, not priority, determines which server should be the Sync Primary and which Sync Servers will start out as Sync Backups or Sync Alternates.
A Sync Local is not assigned a priority because it is not eligible to become a Sync Server, so a Sync Local cannot become a Sync Primary, Sync Backup, or Sync Alternate.
Which Sync Server becomes the Sync Primary in a cluster is determined simply by which Sync Server is started before any of the other servers. The next Sync Servers that start, up to the value in MaxBackups, become Sync Backups. When the Sync Primary fails, the Sync Backup with the highest priority, which is the lowest integer value, becomes the new Sync Primary.
When a Sync Backup becomes a Sync Primary, the number of Sync Backups falls below the value of MaxBackups. To restore the number of Sync Backups, the Sync Alternate with the highest priority becomes a Sync Backup.
Example: Coordination Within a Seven-Server Cluster
The following example illustrates cluster coordination through server roles, and the part that priority plays in determining those roles. As you trace the role changes through the example, keep in mind that server fallibility has been purposely exaggerated to provide many scenarios.Although not required, you can ease cluster maintenance by assigning the highest priority to the iAS machine that you will start as the Sync Primary, and the next highest priorities (in descending order) to the Sync Backups. Be aware that the cluster in this example does not do this. Also, notice that this cluster does not follow the recommended practice of starting the servers in priority order.
Assume a seven-server cluster with iAS machines that are numbered 0 to 6. Servers 0 through 4 are Sync Servers that are assigned the same priorities as their server numbers (for example, server 0 has a priority of zero). Servers 5 and 6 are Sync Locals. MaxBackups for the cluster is set to two.
Server 3 is brought up first, so it becomes the Sync Primary.
Server 3 fails and goes down. Between the two Sync Backups, server 4 and server 1, server 1 has the higher priority (lower integer value) and it becomes the new Sync Primary. This leaves server 4 as the only Sync Backup.Server 4 is started next, and it becomes a Sync Backup.
Server 6 is started next, and it is a Sync Local.
Server 1 is started next, and it becomes a Sync Backup.
Server 2 is started next, and it becomes a Sync Alternate.
Because MaxBackups is set to two, one of the Sync Alternates is converted to a Sync Backup. Server 0 becomes the new Sync Backup because it has a higher priority than the other remaining Sync Alternate, server 2. At this point:
Server 3 comes back online. It becomes a Sync Alternate. Even though it was originally a Sync Primary, the synchronizer now sees it as just another Sync Server, so the server does not resume its Sync Primary role. At this point:
Server 1 is the Sync Primary.
Server 0 fails. Server 2 becomes a Sync Backup because it has the higher priority (lower integer value) among the Sync Alternates. At this point:Servers 0 and 4 are Sync Backups.
Server 1 is the Sync Primary.
Server 0 comes back online and becomes a Sync Alternate. Server 1, the Sync Primary, fails. Among the Sync Backups, server 2 has a higher priority than server 4, so server 2 becomes the new Sync Primary. Server 0 becomes a Sync Backup. At this point:Servers 2 and 4 are Sync Backups.
Server 2 fails. Server 0 becomes the Sync Primary and server 3 becomes a Sync Backup. At this point:
Server 3 fails. Even though only one Sync Backup remains, neither server 5 nor server 6 is considered because neither is a Sync Server. At this point:
Modifying the Default Cluster for Fast Cluster Setup
The fastest and easiest way to set up a cluster is during installation.After installation, the easiest way to set up a cluster is to modify the default cluster that was automatically created when you installed iAS. At installation, the SyncServers kregedit key for the default cluster lists only one server—the server itself. The default cluster is the name of hostname-NoDsync, where hostname is the name of your local machine. For instance, if you install iAS on a machine named "pc543714," the default cluster is pc543714-NoDysnc. The default cluster contains all that a cluster needs to be complete and active except for the new name for the cluster and the names of all Sync Servers with which to synchronize.
Because the default cluster already contains all the kregedit keys that a cluster needs, you can easily set up a cluster by making a few substitutions in the kregedit keys for the default cluster. If you were creating a completely new cluster, you would have to create the kregedit keys for that new cluster.
Entering IP Addresses Using kregedit
When you edit the SyncServers key for the default cluster, you will enter the IP address for each of the Sync Servers in your cluster.At installation, the IP address for each iAS machine is placed in the SyncServers key of that server's default cluster. When you enter the address for each Sync Server into the first SyncServer registry key, remember that you can find the information in the registry for each iAS machine.
Note, however, that you will remove this entry on each Sync Local. If you decide later to promote a Sync Local to a Sync Server, you will have to find the address information elsewhere.
Editing Default Cluster Keys
Sync Locals are never listed in the SyncServers key for a legitimate cluster. But, because each Sync Local is automatically listed in its own default cluster, you must remove each Sync Local from its own SyncServers key.This necessity will be obvious if the cluster settings you edit belong to a Sync Server.
To edit the default cluster keys, perform the following steps:
Stop the application server whose settings you will edit.
After correctly completing these steps, you have redefined the default cluster. Now, follow the procedure in to enable communication between the servers in the cluster.
Open kregedit by typing kregedit at the command prompt.
- Be aware that editing the server registry while the server is running can cause serious problems. Also, some changes take effect only after the engine is recycled.
Open the following folder:
- The kregedit tool displays the keys and values that apply to the iAS machine as shown in the following illustration:
SOFTWARE\iPlanet\Application Server\Clusters\
- In this example, the default cluster is named pc543714-NoDsync and, so far, contains one Sync Server with a priority of zero.
SOFTWARE\iPlanet\Application
Server\Clusters\pc543714-NoDsync\SyncServers
- Whenever one of the following steps directs you to modify a key name or value, you can modify that name or value by performing the following steps:
Double-click the key name to bring up the Modify Value dialog box.
Change the default name (in this case, pc543714-NoDsync) to a new, unique name for your cluster.Enter the new name or value in the dialog box.
Modify the AutoRestartServerForSplitPrimaries, as necessary.
SOFTWARE\iPlanet\Application Server\Clusters\hostname-NoDsync
Check and modify the MaxBackups value, as necessary.
- If set to true (1) then, when the heartbeat mechanism detects a split-primary (dual-primary) server role, the server with the lower priority among the two Sync Primaries is automatically restarted and the abnormal cluster condition is automatically corrected. See step 8 for more information about the heart beat mechanism.
Note You can also set this on the Cluster tab of the General window of the iAS Administration Tool. See Setting Cluster Parameters for more information.
- Note, you can also set this on the Cluster tab of the General window of the iAS Administration Tool.
Check and modify the MaxSyncHeartBeat value, as necessary.
- The maximum number of backup data synchronization servers determines how many Sync Backups are updated with data from the Sync Primary at the same time. For more information about backup data synchronization servers, see
- Because all Sync Backups are updated at the same time, an extra load is created for each additional backup server. Consider the performance impact when you set the number of backups, and try to choose a number that is high enough to provide safety, while not so high as to negatively affect performance. The default value of 1 is usually sufficient.
Note Ignore the MaxHops key. This key relates to an unsupported feature and is now ignored by the server.
- This value specifies the maximum number of heartbeat messages that an engine will send to any other engine. The heart-beat mechanism is used to detect an abnormal cluster condition. Abnormal cluster conditions are defined double-primary (split-primary) and no primary server roles.
- Each heartbeat message consists of the:
Check and modify the SyncHeartBeatInteveral value, as necessary.
- Whenever a heartbeat message is received, an iAS engine will send back a response identifying its role in the cluster.
- A heartbeat starts when a Sync Backup server is promoted to a Sync Primary. The new Sync Primary starts to send heart-beat messages to the original Sync Primary engine. In the case of a temporary network failure, the two engines will become Sync Primaries, thus creating a double-primary (split-primary) abnormal condition. This condition can be automatically corrected. See step 6 for more information.
Check and modify the SyncTimerInterval value, as necessary, which is found in the following location:
- This value specifies the number of seconds between two heartbeat messages sent from one server to another. The default value is 30 seconds.
SOFTWARE\iPlanet\Application Server\Clusters\hostname-NoDsync
Add each Sync Server to the cluster under SyncServers.
- This key specifies the intervals, in seconds, at which the synchronization service wakes up and checks to see whether any data has expired. Specifically, this key specifies how often the timer thread goes through the node list and removes all the nodes that have expired.
- If this value is too large, expired data will still be accessible. If this value is too small, the frequent waking up and checking can degrade system performance. The default value of 60 seconds is good for most clusters.
- The IP addresses and port numbers under the SyncServers key are the Executive Server processes of the iAS machines that belong to this cluster. Each server is listed by its host IP address:KXS port number=priority level.
Add the IP address and port number for the Sync Server.
Set the priority for each Sync Server by double-clicking the priority value to bring up a pop-up window, entering the priority number, and clicking OK. The IP address, port number, and priority for the Sync Server should have been listed under the SyncServers key at installation.
Close kregedit when you have finished.
- The priority setting for a data synchronization server determines which Sync Backup in a group of Sync Backups will become the replacement Sync Primary, and which Sync Alternate in a group of Sync Alternates will become the replacement Sync Backup.
- Priority settings start at zero, the highest priority setting. The lowest priority is 65,535. For more information about priority, see .
Restart all application servers effected by these modifications.
- All changes you make to the SyncServers key now apply to each server in the cluster
Mapping the Synchronizer to the Cluster
For a cluster to communicate, the synchronizer in each server must know to which cluster the synchronizer belongs. This is done by mapping the ClusterName key of each synchronizer to the name of an actual cluster.To map the synchronizer to a cluster, perform the following steps:
Stop the application server whose registry you will edit.
Open kregedit by typing kregedit at the command prompt.
- Be aware that editing the server registry while iAS is running can cause serious problems. Also, some changes take effect only after the engine is recycled.
Open the following key:
SOFTWARE\iPlanet\Application Server\6.0 \CCS0\Clustername
Rename the key under ClusterName to the name of the cluster to which the synchronizer should connect.
- The following example shows the default cluster that has already been renamed "SampleCluster."
SOFTWARE\iPlanet\Application
Server\6.0\CCS0\ClusterName\hostname-NoDsync=0
Close kregedit when you are finished. The synchronizer should now be mapped to the cluster
- If this key has not been previously modified, then the name under ClusterName will be hostname-NoDsync, where hostname is the name of your local machine.
Defining a Cluster
Create a cluster to organize iAS machines into data-synchronizing network-centric groups.Even though each iAS machine can be mapped to only one cluster at a time, you can define as many clusters as you like. Some installations might define multiple clusters for testing purposes, for example.
While you can edit the default cluster to easily set up your first cluster definition, editing the default cluster defines only one cluster. To get more than one definition, create the additional clusters.
To create a cluster, perform the following steps:
Stop the application server whose settings you will edit.
After correctly completing these steps, you have defined a cluster. You can define as many clusters as you like, but you can map the synchronizer to only one cluster at a time. See Mapping the Synchronizer to the Cluster for the procedure that enables communication.
Open kregedit by typing kregedit at the command prompt.
- Be aware that editing the server registry while the server is running can cause serious problems. Also, some changes take effect only after the engine is recycled.
Open the following folder:
- The kregedit tool displays the keys and values that apply to the iAS machine as shown in the following illustration:
SOFTWARE\iPlanet\Application Server\Clusters\
- In this example, the default cluster is named pc543714-NoDsync and, so far, contains one Sync Server with a priority of zero.
SOFTWARE\iPlanet\Application
Server\Clusters\pc543714-NoDsync\SyncServers
- Whenever one of the following steps directs you to modify a key name or value, you can modify that name or value by performing the following steps:
Double-click the key name to bring up the Modify Value dialog box.
Change the default name (in this case, pc543714-NoDsync) to a new, unique name for your cluster.Enter the new name or value in the dialog box.
Check and modify the AutoRestartServerForSplitPrimaries, as necessary.
SOFTWARE\iPlanet\Application Server\Clusters\hostname-NoDsync
Check and modify the MaxBackups value, as necessary.
- If set to true (1) then, when the heartbeat mechanism detects a split-primary (dual-primary) server role, the server with the lower priority among the two Sync Primaries is automatically restarted and the abnormal cluster condition is automatically corrected. See step 8 for more information about the heart beat mechanism.
Check and modify the MaxSyncHeartBeat value, as necessary.
- The maximum number of backup data synchronization servers determines how many Sync Backups are updated with data from the Sync Primary at the same time. For more information about backup data synchronization servers, see
- Because all Sync Backups are updated at the same time, an extra load is created for each additional backup server. Consider the performance impact when you set the number of backups, and try to choose a number that is high enough to provide safety, while not so high as to negatively affect performance. The default value of 1 is usually sufficient.
Note Ignore the MaxHops key. This key relates to an unsupported feature and is now ignored by the server.
- This value specifies the maximum number of heartbeat messages that an engine will send to any other engine. The heartbeat mechanism is used to detect an abnormal cluster condition. Abnormal cluster conditions are defined double-primary (split-primary) and no primary server roles.
- Each heartbeat message consists of the:
Check and modify the SyncHeartBeatInteveral value, as necessary.
- Whenever a heartbeat message is received, an iAS engine will send back a response identifying its role in the cluster.
- A heartbeat starts when a Sync Backup server is promoted to a Sync Primary. The new Sync Primary starts to send heart-beat messages to the original Sync Primary engine. In the case of a temporary network failure, the two engines will become Sync Primaries, thus creating a double-primary (split-primary) abnormal condition. This condition can be automatically corrected. See step 6 for more information.
Check and modify the SyncTimerInterval value, as necessary, which is found in the following location:
- This value specifies the number of seconds between two heartbeat messages sent from one server to another. The default value is 30 seconds.
SOFTWARE\iPlanet\Application Server\Clusters\hostname-NoDsync
Add each Sync Server to the cluster under SyncServers.
- This key specifies the intervals, in seconds, at which the synchronization service wakes up and checks to see whether any data has expired. Specifically, this key specifies how often the timer thread goes through the node list and removes all the nodes that have expired.
- If this value is too large, expired data will still be accessible. If this value is too small, the frequent waking up and checking can degrade system performance. The default value of 60 seconds is good for most clusters.
- The IP addresses and port numbers under the SyncServers key are the Executive Server processes of the iAS machines that belong to this cluster. Each server is listed by its host IP address:KXS port number=priority level.
Add the IP address and port number for the Sync Server.
Set the priority for each Sync Server by double-clicking the priority value to bring up a pop-up window, entering the priority number, and clicking OK. The IP address, port number, and priority for the Sync Server should have been listed under the SyncServers key at installation.
Close kregedit when you have finished.
- The priority setting for a data synchronization server determines which Sync Backup in a group of Sync Backups will become the replacement Sync Primary, and which Sync Alternate in a group of Sync Alternates will become the replacement Sync Backup.
- Priority settings start at zero, the highest priority setting. The lowest priority is 65,535. For more information about priority, see .
Restart all application servers effected by these modifications.
- All changes you make to the SyncServers key now apply to each server in the cluster
Using the Administration Tool to Configure Clusters
You can perform the following tasks to configure clusters using iPlanet Application Server (iAS) Administration Tool:
Creating a Cluster
Note that to properly configure a cluster using iAS Administration Tool, you must register all the servers in the cluster. Otherwise, configuration changes will not apply across all the servers in the cluster.Removing a Server from a Cluster
For information about editing cluster settings directly, see the various sections earlier in this chapter that discuss how to configure clusters.
Creating a Cluster
To create a new cluster, perform the following steps:
From the iAS Administration Tool toolbar, click the General button to open the General window.
After you restart the server, you can add iAS machines to the new cluster as described in the following section.In the right pane of the General window, click the Cluster tab.
Highlight the Cluster Name to select hostname-No-Dsync.
Use the Delete key on your keyboard to clear the Cluster Name drop-down box.
Type the name of your new cluster in the Cluster Name drop-down box and press the Enter key on your keyboard.
Click Apply Changes.
- You can choose any unique name for the new cluster.
- Your changes do not take effect until you restart the server.
Adding a Server to a Cluster
To add an unassigned server to a cluster, or to reassign a server to a different cluster, perform the following steps:
From the iAS Administration Tool toolbar, click the General button to open the General window.
In the left pane of the General window, click the name of the server you want to add to a cluster.
- The following window appears:
- A list of all registered servers is displayed in the left pane of the General window. Another list of servers, sorted by priority in a cluster, is displayed in the right pane as shown in the previous illustration.
- The Priority List of Servers box also shows the cluster status of the server. Server conditions can be Normal, Dual Primary or No Primary. You can click the Refresh List button to immediately update the Priority List of Servers box. By default, this box is updated every 15 seconds.
From the Cluster Name drop-down box, select the name of the cluster you want to add the server to.
- A server that is not a member of a cluster, hence not participating in data synchronization, is listed under hostname-NoDsync, in the cluster list on the right.
Click Apply Changes.
- The Cluster Name drop-down list is populated with the cluster names that all registered servers belong to. If the servers in a cluster are not registered by iAS Administration Tool, then that cluster does not appear in the Cluster Name drop-down box. For the name of a cluster to appear in Cluster Name, you must register one or more of the servers in that cluster.
Shut down and restart every server in the cluster, including the server you just added. For changes to apply across the cluster, you must restart every machine to reload the memory on each machine with the cluster configuration changes. If at least one machine has a different cluster configuration loaded into memory than the other machines in the cluster, the new settings will not take effect and data synchronization will not work properly.
If when adding the server to a cluster, you removed it from another, you must also shut down and restart every server in the cluster from which it was removed.
Removing a Server from a Cluster
To remove a server from a cluster, perform the following steps:
From the iAS Administration Tool toolbar, click the General button to open the General window.
Click the Clusters tab to display the following window:
In the left pane of the General window, click the name of the server you want to remove from the cluster.
- A list of registered servers is displayed in the left pane of the General window. Another list of servers, sorted by priority in a cluster, is displayed in the right pane.
Click Remove from Cluster.
- You can remove a server from a cluster only when it is assigned to a cluster and registered with iAS Administration Tool. A server that is not a member of a cluster, hence not participating in data synchronization, is listed under hostname-NoDsync, in the cluster list. You cannot remove a server from the hostname-NoDsync list.
- Note that you cannot remove an unregistered server from a cluster.
Shut down and restart every server in the cluster, including the server you just removed. For changes to apply across the cluster, you must restart every machine to reload the memory on each machine with the cluster configuration changes. If at least one machine has a different cluster configuration loaded into memory than the other machines in the cluster, the new settings will not take effect and data synchronization will not work properly.
Changing Sync Server Priority
To assign a new Sync Server priority to a server that is in a cluster, perform the following steps:
From the iAS Administration Tool toolbar, click the General button to open the General window.
Click the Clusters tab to display the following window:
In the left pane of the General window, click a server that is a member of the cluster whose Sync Server priority you want to change.
- A list of registered servers is displayed in the left pane of the General window. Another list of servers, sorted by priority in a cluster, is displayed in the right pane.
- The list also shows the status of each machine in the cluster. The status should always be "Normal." If an abnormal cluster condition exists, it could also show "Dual Primary" or "No Primary." To ensure that these conditions are corrected, see Setting Cluster Parameters. The Refresh List button causes iAS Administration Tool to immediately check for status. Normally it checks every 15 seconds.
In the Priority List text box, click the name of the server whose Sync Server priority you want to change.
Click one of the following:
- You can change Sync Server priority order only for a registered server that belongs to a cluster. A server that is not a member of a cluster, hence not participating in data synchronization, is listed under hostname-NoDsync, in the cluster list on the right.
When you finish reassigning priorities, click Apply Changes.
- Click as many times as you want to increase or decrease the priority. For example, if a server has a Sync Server priority of third in line to take over for the Sync Primary, clicking Increase once changes the priority from third to second.
Restart every server in the cluster, including the one whose priority you just changed. For changes in Sync Server priority to apply across a cluster, you must restart every machine so that they are all aware of their new priority sequence, relative to one another.
Setting Cluster Parameters
You can set the following cluster parameters:You can specify the maximum number of Sync Backups the Sync Primary will use. In clusters of numerous machines, this allows you to control how many other machines are used as backups.
You can also enable the appropriated process to restart in case an abnormal cluster condition is detected. An abnormal cluster condition is either a cluster that has more than one iAS machines with the Sync Primary (dual-primary) role or no iAS machines with the Sync Primary role.
To set the cluster parameters, perform the following steps:
From the iAS Administration Tool toolbar, click the General button to open the General window.
Restart every server in the cluster. For changes to apply across a cluster, you must restart every machine so that they are all aware of the changes.Click the Clusters tab to display the following window:
In the left pane of the General window, click the name of a server that is a member of the cluster you want to modify.
Enter the maximum number of Sync Backups allowed during a single cluster session in Maximum Number of Sync Backups.
Check the Restart in case of abnormal cluster to correct any abnormal cluster conditions that are detected.
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Last Updated September 05, 2000