replication

Clarifications

Considerations for Using Peer-to-Peer Replication

This section provides information and guidelines to consider when you use peer-to-peer replication.
General Considerations

* Peer-to-peer replication is available only in SQL Server 2008 Enterprise.
* All databases that participate in peer-to-peer replication should contain identical schema and data:
o Object names, object schema, and publication names should be identical.
o Publications must allow schema changes to be replicated. (This is a setting of 1 for the publication property replicate_ddl, which is the default setting.) For more information, see Making Schema Changes on Publication Databases.
o Row and column filtering are not supported.
* We recommend that each node use its own distribution database. This eliminates the potential of having a single point of failure.
* Tables and other objects cannot be included in multiple peer-to-peer publications in a single publication database.
* A publication must be enabled for peer-to-peer replication before any subscriptions are created.
* Subscriptions must be initialized by using a backup or with the 'replication support only' option. For more information, see Initializing a Transactional Subscription Without a Snapshot.
* We do not recommend the use of identity columns. When using identities, you must manually manage the ranges assigned to the tables at each participating database. For more information, see the section "Assigning Ranges for Manual Identity Range Management" in Replicating Identity Columns.

Feature Restrictions

Peer-to-peer replication supports the core features of transactional replication, but does not support the following options:

* Initialization and reinitialization with a snapshot.
* Row and column filters.
* Timestamp columns.
* Non-SQL Server Publishers and Subscribers.
* Immediate updating and queued updating subscriptions.
* Anonymous subscriptions.
* Partial subscriptions.
* Attachable subscriptions and transformable subscriptions. (Both of these options were deprecated in SQL Server 2005.)
* Shared Distribution Agents.
* The Distribution Agent parameter -SubscriptionStreams and the Log Reader Agent parameter -MaxCmdsInTran.
* The article properties @destination_owner and @destination_table.

The following properties have special considerations:

* The publication property @allow_initialize_from_backup requires a value of true.
* The article property @replicate_ddl requires a value of true; @identityrangemanagementoption requires a value of manual; and @status requires that option 24 is set.
* The value for article properties @ins_cmd, @del_cmd, and @upd_cmd cannot be set to SQL.
* The subscription property @sync_type requires a value of none or automatic.

Maintenance Considerations

The following actions require the system to be quiesced. This means stopping activity on published tables at all nodes and making sure that each node has received all changes from all other nodes.

* Adding a SQL Server 2005 node to an existing topology
* Adding an article to an existing publication
* Making schema changes
* Restoring a node from a backup
http://msdn.microsoft.com/en-us/library/ms152536.aspx

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