Core group protocol versions

Core group members interact with each other through a variety of protocols such as the discovery protocol, the failure detection protocol, and the view synchrony protocol. Each of these protocols define a set of formatted messages that core group members exchange according to a common algorithm.

Note: This topic references one or more of the application server log files. As a recommended alternative, you can configure the server to use the High Performance Extensible Logging (HPEL) log and trace infrastructure instead of using SystemOut.log , SystemErr.log, trace.log, and activity.log files on distributed and IBM® i systems. You can also use HPEL in conjunction with your native z/OS® logging facilities. If you are using HPEL, you can access all of your log and trace information using the LogViewer command-line tool from your server profile bin directory. See the information about using HPEL to troubleshoot applications for more information on using HPEL.

New protocol versions are added to the product if new messages, or new algorithms are required to support new product features, or to improve core group performance. Because the new messages or new algorithm might not be compatible with the older messages or algorithm, a new protocol might not be able to interoperate with the previous version of the protocol.

Avoid trouble: The highest protocol versions are used by default instead of older versions as specified by previous WebSphere releases. The following custom properties can be used to revert back to older protocol versions; however, this is not recommended.
Mixed-version environment: To maintain compatibility in a mixed cell environment, the following custom properties must be explicitly set to use the highest protocol levels.
There are two major categories or groups of protocols.
  • A collection of lower-level protocols, which are also referred to as the lower-level wire format protocols. These protocols are used by the DCS layer. The setting for the IBM_CS_WIRE_FORMAT_VERSION core group custom property determines which protocol version is used for this group of protocols.
    Whenever the value specified for this property changes, an HMGR0226I message, similar to the following example, is sent to the SystemOut.log file, or, for the z/OS platform, to either SYSOUT or SYSPRINT: 
    HMGR0226I: The core stack configuration parameter IBM_CS_WIRE_FORMAT_VERSION has been set to 6.1.0.
  • A collection of higher level protocols, which are also referred to as the high availability manager protocols. These protocols are used by the high availability manager layer. The setting for the IBM_CS_HAM_PROTOCOL_VERSION core group custom property determines which protocol version is used for this group of protocols.
    Whenever the value specified for this property changes, a HMGR0226I message, similar to the following message, is sent to the SystemOut.log file, or, for the z/OS platform, to either SYSOUT or SYSPRINT:
    HMGR0226I: The core stack configuration parameter IBM_CS_HAM_PROTOCOL_VERSION 
   has been set to 6.0.2.31.

    This message indicates that the high availability manager protocol version 6.0.2.31 is being used.

The protocol version settings for each of these two categories are independent of each other.

When to use an older core group protocol version

It is not recommended to use an older core group protocol version. The only time when this is needed is in a Core group containing a mix of Version 9 servers and servers on Version 7.0.0.0 or earlier.

Using the high availability manager protocol to establish transparent bridge failover support

Core group bridges provide the mechanism that is used to represent and manage the cross core group state that is used by WebSphere® Application Server components. Part of the management process for this cross-core group state is to perform core group bridge state rebuilds whenever there is a change in the number of running core group bridges in a topology. The core group bridge state rebuild is the means by which core group bridges calculate the ownership, and distribution of the cross-core group state among the running set of bridges.

During core group bridge state rebuilds, cross-core group state can be moved between running bridges. This situation might cause the data to be temporarily unavailable until the bridge has completed the rebuild process. Common symptoms of this problem include:
  • JNDI lookups failing.
  • A WebSphere proxy server, or on-demand router generates a 503 response code after a core group bridge failover occurs
  • The following array index out-of-bounds exception occurs: 
    [7/9/08 17:12:20:749 EDT] 00000030 UserCallbacks E 
HMGR0142E: An error occurred in a component called back by the High Availability Manager 
The exception is java.lang.ArrayIndexOutOfBoundsException at
com.ibm.ws.cluster.propagation.bulletinboard.BBDescriptionManager.getOrderedBytes(BBDescriptionManager.java:618)
Best practice: If you are running on Version 7.0.0.1 to Version 8.5.5.X, set the IBM_CS_HAM_PROTOCOL_VERSION core group custom property to 6.0.2.31 for all of your core groups to avoid a possible high availability state outage during core group bridge failover. When this custom property is set to 6.0.2.31, the remaining bridges recover the high availability state of the failed bridge without the data being unavailable in the local core group.
Avoid trouble:
  • Ensure that all core groups that are connected with core group bridges are running the same protocol version.
  • Transparent bridge failover is designed to hold state data constant during core group bridge rebuilds along the state data path, which is the path that consists of the state provider, one core group bridge in each respective core group, and a state data consumer. Failure scenarios involving core groups with no remaining active bridges might still result in temporary state outages.

Determining which protocol version to use

Avoid trouble: Use the newest protocol version whenever possible (this is the default in Version 9). This practice is especially critical for large topologies because most of the recent protocol changes include scalability improvements. However, before configuring the members of a core group to use a new protocol version, you must verify that all of the core group members are running at a product code level (VRM) that is equal to or greater than the VRM in which the desired protocol version was added to the product. For example:
  • A core group that contains core group members at any supported VRM can be configured to use the Version 6.0.0, 6.0.2.9, or 6.1.0 wire format protocol.
  • A core group that contains a mix of Version 6.1.0.19 and 7.0.0.1 core group members can be configured to use the Version 6.0.2.31 high availability manager protocol.

Supported core group protocol version IDs

The following tables summarize for each protocol category the minimum level of the product that core group members must be running at before they can be associated with a specific protocol version. These tables also describe the new capabilities that were added in each protocol version.

Use these tables to determine which protocol versions you can use with a particular core group, and then use either the IBM_CS_WIRE_FORMAT_VERSION or the IBM_CS_HAM_PROTOCOL_VERSION core group custom property to configure all of the members of that core group to run using the newest of those protocol versions that are supported by the level of the product on which you are running. The high availability manager automatically detects the configuration changes and starts to use the new core group protocol version with these core group members.

Deprecated feature: Wire format protocol versions 6.0.0 and 6.0.2.9 are deprecated. Whenever possible you should use a newer protocol version.
Table 1. Supported wire format protocol version IDs . The protocol version ID indicates the first version, release, and modification level in which that version is included. The following table lists the supported wire format protocol version IDs.
Version ID Required Minimum product Level Description
6.0.0 Any This protocol version is the original or base version. All versions of the high availability manager can use this protocol. If you do not specify a particular wire format protocol version, the high availability manager uses this version.
6.0.2.9 Any supported version This protocol version facilitates core group bridge scalability. This version is recommended for large topologies that contain multiple core groups and core group bridges as part of their configuration.
6.1.0 Any supported version This version adds core group scalability improvements, and more support for large topologies.
Table 2. Supported high availability manager protocol version IDs . The protocol version ID indicates the first version, release, and modification level in which that version is included. The following table lists the supported high availability manager protocol version IDs.
Version ID Required Minimum product Level Description
6.0.2.31 6.1.0.19 for Version 6.1, 7.0.0.1 for Version 7.0, and the initial release of any later versions of the product This protocol version is the original or base version of the high availability manager protocol, and is available in any supported version of the product to facilitate core group bridge scalability. This protocol version is recommended for topologies that contain multiple core groups and core group bridges as part of their configuration. You must specify the high availability manager protocol version for the high availability manager to use the protocol. There is no default version.