All datasources within a dataservice have a specific role within he
dataservice. The Primary role is
one that provides a source of replication information, and a Replica one
that receives that information.
| Role | Supplies Replication Data | Receives Replication Data | Load Balancing | Failover |
|---|---|---|---|---|
Master
| Yes | No | Yes | Yes |
Slave
| No | Yes | Yes | Yes |
Standby
| No | Yes | No | Yes |
Archive
| No | Yes | Yes | No |
More detailed information for each role:
A datasource in a Primary role
is providing a source for replication information to other datasources
in the dataservice and is able to provide both read and write
connections for applications.
A Replica datasource is
receiving data from a Primary
and having that replicated data applied by Tungsten Cluster. Replicas are
used for read-only operations by applications.
A standby datasource receives
replication data, but is never chosen by the connector to act as a
read source by application clients. Standby datasources are therefore
kept up to date with replication, but not used for load balancing.
When a failover occurs, a
standby datasource can be
enabled as a standard Replica
and included in load-balanced operations.
An archive datasource can be
used to provide an active (up to date) copy of the data, without the
datasource being used in the event of a failover. This can be useful
for providing backup support, offline querying outside of the normal
dataservice operations, or auditing purposes.