Core groups (high availability domains)
A core group is a high availability domain that consists of a set of processes in the same cell.
- HA components can only fail over to another process in the same core group
- Replication can occur only between members of the same core group
A cell must contain at least one core group. Multiple core groups are supported. Each core group contains...
- A core group coordinator to manage its HA relationships
- A set of HA policies
Core group members
Core group members include...
- dmgr
- node agent
- appserver
- proxy server
When a process is created it is automatically added to a core group. We can move processes from one core group to another.
Rules...
- Every process is a member of exactly one core group.
- All members of a cluster must be members of the same core group.
Life cycle...
- First core group member starts
- The transport dedicated to the core group automatically starts...
- The Discovery Protocol...
- Discovers when other core group processes start
- Opens network connections to core group members
- The View Synchrony Protocol exchanges state information between members.
- The Failure Detection Protocol monitors the core group network connections that the Discovery Protocol establishes.
The V6.0.x and v6.1.x requirement that every core group must contain at least one node agent or the dmgr does not apply to WAS ND v7. However, if we are running in a mixed cell environment, every core group that contains any V6.x members must also contain at least one node agent or the dmgr.
Core group coordinator
The core group coordinator is responsible for coordinating HA activities between the core group members for which View Synchrony Protocol is established.
Core group transport
Network communication between all the members of a core group must consist of a fast LAN with full IP visibility and bidirectional communication between all core group members.
Each core group member must be able to receive communications from any of the other core group members.
Multiple core groups
A cell, by default, contains a single core group, DefaultCoreGroup, of which all processes in the cell are initially members. A single core group is usually sufficient.
Configure multiple core groups when...
- A large number of processes in the cell, and core group protocols such as View Synchrony Protocol, consume large amounts of memory and CPU.
- Core group protocols such as Failure Detection Protocol need tuning to use values that work best with smaller numbers of core group members.
For different core groups to share workload management or on-demand configuration routing information, use the core group bridge service to create access point groups to for connecting the core groups.
Subtopics
Core group migration considerations
Core group coordinator
Core group administration considerations
Core group scaling considerations
Core group View Synchrony Protocol
Core group discovery and failure detection protocols
Core group protocol versions
Related concepts
Core group communications using the core group bridge service
High availability manager
Related tasks
Change the number of core group coordinators
Configure core group preferred coordinators
Configure the default Discovery Protocol for a core group
Configure the default Failure Detection Protocol for a core group
Configure a core group transport
Create a new core group (HA domain)
Moving core group members