The dataservice operates using a policy mode, which configures how the dataservice management system responds to different events and operations within the dataservice. The policy mode can be set at will and enables maintenance and administration to be carried out without triggering the automatic failure and recovery procedures for operations that would otherwise trigger an automated response.
The procedure for how these operations are carried out are defined through a series of rules, with different policies applying different sets of the individual rules. The setting of the policy mode is dataservice-wide and instantaneous.
The individual policy modes are described below:
AUTOMATIC Policy Mode
In automatic mode, the following operations and status changes happen automatically, managed by the coordinator:
Failed slave datasources are automatically marked as failed, temporarily removed from the dataservice, with application connections redirect to the other nodes in the dataservice. When the datasource becomes available, the node is automatically recovered to the dataservice.
Failed master datasources are automatically shunned and switched to the most up to date slave within the dataservice, which becomes the master and remaining slaves point to the newly promoted master.
Automatic policy mode operates within a single dataservice only. Within a composite dataservice there is no automatic failover.
MANUAL Policy Mode
MANUAL policy mode, the
dataservice identifies and isolates datasources when they fail, but
automatic failover (for master datasources) and recovery is disabled.
MAINTENANCE Policy Mode
MAINTENANCE policy mode all
rules are disabled. Maintenance mode should be used when performing
datasource or host maintenance that would otherwise trigger an automated
fencing or recovery process.
Maintenance mode should be used when administration or maintenance is required on the datasource, software, or operating system.
To set the policy, use the set command with the policy option. For example, to switch the current dataservice policy mode to manual:
[LOGICAL:EXPERT] /alpha >
set policy manualpolicy mode is now MANUAL
Policy mode changes are global, affecting the operation of all the members of the dataservice.