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sys.availability_replicas (Transact-SQL)

Returns a row for each of the availability replicas that belong to any AlwaysOn availability group in the WSFC failover cluster.

If the local server instance is unable to talk to the WSFC failover cluster, for example because the cluster is down or quorum has been lost, only rows for local availability replicas are returned. These rows will contain only the columns of data that are cached locally in metadata.

Applies to: SQL Server (SQL Server 2012 through current version).

Column name

Data type

Description

replica_id

uniqueidentifier

Unique ID of the replica.

group_id

uniqueidentifier

Unique ID of the availability group to which the replica belongs.

replica_metadata_id

int

ID for the local metadata object for availability replicas in the Database Engine.

replica_server_name

nvarchar(256)

Server name of the instance of SQL Server that is hosting this replica and, for a non-default instance, its instance name.

owner_sid

varbinary(85)

Security identifier (SID) registered to this server instance for the external owner of this availability replica.

NULL for non-local availability replicas.

endpoint_url

nvarchar(128)

String representation of the user-specified database mirroring endpoint that is used by connections between primary and secondary replicas for data synchronization. For information about the syntax of endpoint URLs, see Specify the Endpoint URL When Adding or Modifying an Availability Replica (SQL Server).

NULL = Unable to talk to the WSFC failover cluster.

To change this endpoint, use the ENDPOINT_URL option of ALTER AVAILABILITY GROUP Transact-SQL statement.

availability_mode

tinyint

The availability mode of the replica, one of:

Value

Meaning

0

Asynchronous commit. The primary replica can commit transactions without waiting for the secondary to write the log to disk.

1

Synchronous commit. The primary replica waits to commit a given transaction until the secondary replica has written the transaction to disk.

For more information, see Availability Modes (AlwaysOn Availability Groups).

availability_mode_desc

nvarchar(60)

Description of availability_mode, one of:

ASYNCHRONOUS_COMMIT

SYNCHRONOUS_COMMIT

To change this the availability mode of an availability replica, use the AVAILABILITY_MODE option of ALTER AVAILABILITY GROUP Transact-SQL statement.

failover_mode

tinyint

The failover mode of the availability replica, one of:

Value

Meaning

0

Manual failover. A failover to a secondary replica set to manual failover must be manually initiated by the database administrator. The type of failover that is performed will depend on whether the secondary replica is synchronized, as follows:

  • If the availability replica is not synchronizing or is still synchronizing, only forced failover (with possible data loss) can occur.

  • If the availability mode is set to synchronous commit (availability_mode = 1) and the availability replica is currently synchronized, manual failover without data loss can occur.

1

Automatic failover. The replica is a potential target for automatic failovers. Automatic failover is supported only if the availability mode is set to synchronous commit (availability_mode = 1) and the availability replica is currently synchronized.

To view a rollup of the database synchronization health of every availability database in an availability replica, use the synchronization_health and synchronization_health_desc columns of the sys.dm_hadr_availability_replica_states dynamic management view. The rollup considers the synchronization state of every availability database and the availability mode of its availability replica.

Tip Tip

To view the synchronization health of a given availability database, query the synchronization_state and synchronization_health columns of the sys.dm_hadr_database_replica_states dynamic management view.

failover_mode_desc

nvarchar(60)

Description of failover_mode, one of:

MANUAL

AUTOMATIC

To change the failover mode, use the FAILOVER_MODE option of ALTER AVAILABILITY GROUP Transact-SQL statement.

session_timeout

int

The time-out period, in seconds. The time-out period is the maximum time that the replica waits to receive a message from another replica before considering connection between the primary and secondary replica have failed. Session timeout detects whether secondaries are connected the primary replica.

On detecting a failed connection with a secondary replica, the primary replica considers the secondary replica to be NOT_SYNCHRONIZED. On detecting a failed connection with the primary replica, a secondary replica simply attempts to reconnect.

Note Note

Session timeouts do not cause automatic failovers.

To change this value, use the SESSION_TIMEOUT option of ALTER AVAILABILITY GROUP Transact-SQL statement.

primary_role_allow_connections

tinyint

Whether the availability allows all connections or only read-write connections, one of:

2 = All (default)

3 = Read write

primary_role_allow_connections_desc

nvarchar(60)

Description of primary_role_allow_connections, one of:

ALL

READ_WRITE

secondary_role_allow_connections

tinyint

Whether an availability replica that is performing the secondary role (that is, a secondary replica) can accept connections from clients, one of:

0 = No. No connections are allowed to the databases in the secondary replica, and the databases are not available for read access. This is the default setting.

1 = Read only. Only read-only connections are allowed to the databases in the secondary replica. All database(s) in the replica are available for read access.

2 = All. All connections are allowed to the databases in the secondary replica for read-only access.

For more information, see Active Secondaries: Readable Secondary Replicas (AlwaysOn Availability Groups).

secondary_role_allow_connections_desc

nvarchar(60)

Description of secondary_role_allow_connections, one of:

NO

READ_ONLY

ALL

create_date

datetime

Date that the replica was created.

NULL = Replica not on this server instance.

modify_date

datetime

Date that the replica was last modified.

NULL = Replica not on this server instance.

backup_priority

int

Represents the user-specified priority for performing backups on this replica relative to the other replicas in the same availability group. The value is an integer in the range of 0..100.

For more information, see Active Secondaries: Backup on Secondary Replicas (AlwaysOn Availability Groups).

read_only_routing_url

nvarchar(256)

Connectivity endpoint (URL) of the read only availability replica. For more information, see Configure Read-Only Routing for an Availability Group (SQL Server).

Permissions

Requires VIEW ANY DEFINITION permission on the server instance.

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