coregroupsplit.py script

You can use the coregroupsplit.py script to split your existing cell into multiple core groups. Consider running this script if you have more than 40 WebSphere® Application Server related processes such as application servers, node agents, and on demand routers (ODRs) defined in your core group.

Purpose

The coregroupsplit.py script divides your existing cell into multiple core groups. If a server changes its core group membership, then you must restart the entire cell to prevent partitions from forming. For this reason, the default options used by this script do not change the core group membership of servers that are members of any core groups other than DefaultCoreGroup.

Running the script attempts to satisfy the following best practices for core groups:

Each core group must have fewer than 40 servers. This best practice is possible only when you have an adequate ratio of nodes to servers in your cell.
Each core group must be equipped with at least three core group bridges. This best practice is possible only when you have an adequate ratio of nodes to servers in your cell.
Each cluster must remain fully mapped to a single core group.
If you use the -createbridges parameter, the core group bridges and coordinators are preferably hosted on otherwise idle nodes.

This script also tunes the high availability manager for optimum performance. By default, the script configures a core group bridge on each node agent in the cell. The script increases the number of core groups until it reaches the optimal level, depending on the number of nodes and servers in the cell. The core group bridge node agents are configured as a part of the DefaultAccessPointGroup access point group in a mesh topology. In the preferred mesh topology, all of the access points are collected into a single access point group. As a result, all bridge interfaces can directly intercommunicate.

Remember that you must give core group bridges at least 512 MB of Java™ virtual machine (JVM) space.

Location

The coregroupsplit.py script is in the app_server_root/bin directory.

Usage

The default script usage follows:

./wsadmin.sh -lang jython -f coregroupsplit.py

Running this script might result in unbalanced core groups, in which some core groups are loaded more or less than other core groups. You can rerun this script to rebalance core group membership, but in this case you must restart the entire cell for the changes to take effect. To rerun the script, use the following command:

./wsadmin.sh -lang jython -f coregroupsplit.py -reconfig

Parameters

-reconfig: Performs a full reconfiguration to rebalance the distribution of servers among the core groups.
-linked: Creates a ring topology of core group bridges.
-createbridges: Creates separate core group bridge processes instead of creating the bridge in the node agent.
-numcoregroups: Specifies the number of core groups to create.
-datastacksize: Specifies a number of megabytes that overrides the default data stack size.
-proxycoregroup: Places the on demand routers (ODR) and proxy servers in a separate core group.
-odrcoregroup: Places the on demand routers (ODR) and proxy servers in a separate core group.
-nosave: Does not save any changes made to the core group. You can use this option to test setting parameters and running the script.
-debug: Prints troubleshooting information.
-nodesPerCG:number: Specifies the number of node agents that are required for each core group.
-numberOfServersPerCG:number: Specifies the maximum number of servers for each core group.
-bridgeHeapSize:number: Specifies the server heap size of the core group bridge in megabytes.

Examples

The following example results in a linked topology where the core group bridges are connected in a ring:

./wsadmin.sh -lang jython coregroupsplit.py -linked

You can also use this script to create static cluster that are dedicated as core group bridges for communication within the core group. Use the following example:

./wsadmin.sh -lang jython coregroupsplit.py -createbridges