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Implement a Custom Conflict Resolver for a Merge Article

This topic describes how to implement custom conflict resolver for a merge article in SQL Server 2012 by using Transact-SQL or a COM-based custom resolver.

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You can write your own custom conflict resolver as a Transact-SQL stored procedure at each Publisher. During synchronization, this stored procedure is invoked when conflicts are encountered in an article to which the resolver was registered, and information on the conflict row is passed by the Merge Agent to the required parameters of the procedure. Stored procedure-based custom conflict resolvers are always created at the Publisher.

Note Note

Microsoft SQL Server stored procedure resolvers are only invoked to handle row change-based conflicts. They cannot be used to handle other types of conflicts such as insert failures due to PRIMARY KEY violations or unique index constraint violations.

To create a stored procedure-based custom conflict resolver

  1. At the Publisher in either the publication or msdb database, create a new system stored procedure that implements the following required parameters:

    Parameter

    Data type

    Description

    @tableowner

    sysname

    Name of the owner of the table for which a conflict is being resolved. This is the owner for the table in the publication database.

    @tablename

    sysname

    Name of the table for which a conflict is being resolved.

    @rowguid

    uniqueidentifier

    Unique identifier for the row having the conflict.

    @subscriber

    sysname

    Name of the server from where a conflicting change is being propagated.

    @subscriber_db

    sysname

    Name of the database from where conflicting change is being propagated.

    @log_conflict OUTPUT

    int

    Whether the merge process should log a conflict for later resolution:

    0 = Do not log the conflict.

    1 = Subscriber is the conflict loser.

    2 = Publisher is the conflict loser.

    @conflict_message OUTPUT

    nvarchar(512)

    Message to be given about the resolution if the conflict is logged.

    @destowner

    sysname

    The owner of the published table at the Subscriber.

    This stored procedure uses the values passed by the Merge Agent to these parameters to implement your custom conflict resolution logic; it must return a single row result set that is identical in structure to the base table and contains the data values for the winning version of the row.

  2. Grant EXECUTE permissions on the stored procedure to any logins used by Subscribers to connect to the Publisher.

To use a custom conflict resolver with a new table article

  • Execute sp_addmergearticle to define an article, specifying a value of MicrosoftSQL Server Stored Procedure Resolver for the @article_resolver parameter and the name of the stored procedure that implements the conflict resolver logic for the @resolver_info parameter. For more information, see Define an Article.

To use a custom conflict resolver with an existing table article

  1. Execute sp_changemergearticle, specifying @publication, @article, a value of article_resolver for @property, and a value of MicrosoftSQL Server Stored Procedure Resolver for @value.

  2. Execute sp_changemergearticle, specifying @publication, @article, a value of resolver_info for @property, and the name of the stored procedure that implements the conflict resolver logic for @value.

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The Microsoft.SqlServer.Replication.BusinessLogicSupport namespace implements an interface that enables you to write complex business logic to handle events and resolve conflicts that occur during the merge replication synchronization process. For more information, see Implement a Business Logic Handler for a Merge Article.You can also write your own native code-based custom business logic to resolve conflicts. This logic is built as a COM component and compiled into dynamic-link libraries (DLL), using products such as Microsoft Visual C++. Such a COM–based custom conflict resolver must implement the ICustomResolver interface, which is designed specifically for conflict resolution.

To create and register a COM-based custom conflict resolver

  1. In a COM-compatible authoring environment, add references to the Custom Conflict Resolver library.

  2. For a Visual C++ project, use the #import directive to import this library into your project.

  3. Create a class that implements the ICustomResolver interface.

  4. Implement certain methods and properties.

  5. Build the project to create the custom conflict resolver library file.

  6. Deploy the library in the directory containing the merge agent executable (usually \Microsoft SQL Server\100\COM).

    Note Note

    A custom conflict resolver must be deployed at the Subscriber for a pull subscription, at the Distributor for a push subscription, or at the Web server used with Web synchronization.

  7. Register the custom conflict resolver library using regsvr32.exe from the deployment directory as follows:

    regsvr32.exe mycustomresolver.dll
    
  8. At the Publisher, execute sp_enumcustomresolvers (Transact-SQL) to verify that the library is not already registered as a custom conflict resolver.

  9. To register the library as a custom conflict resolver, execute sp_registercustomresolver (Transact-SQL), at the Distributor. Specify the friendly name of the COM object for @article_resolver, the library's ID (CLSID) for @resolver_clsid, and a value of false for @is_dotnet_assembly.

    Note Note

    When no longer needed, a custom conflict resolver can be unregistered using sp_unregistercustomresolver (Transact-SQL).

  10. (Optional) On a cluster, repeat steps 5-8 to register the custom resolver on all nodes of the cluster. This is required to ensure that the custom resolver will be able to properly load the reconciler following a failover.

To use a custom conflict resolver with a new table article

  1. At the Publisher, execute sp_enumcustomresolvers (Transact-SQL) and note the friendly name of the desired resolver.

  2. At the Publisher on the publication database, execute sp_addmergearticle (Transact-SQL) to define an article. Specify the friendly name of the article resolver from step 1 for @article_resolver. For more information, see Define an Article.

To use a custom conflict resolver with an existing table article

  1. At the Publisher, execute sp_enumcustomresolvers (Transact-SQL) and note the friendly name of the desired resolver.

  2. Execute sp_changemergearticle (Transact-SQL), specifying @publication, @article, a value of article_resolver for @property, and the friendly name of the article resolver from step 1 for @value.

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Viewing a Sample Custom Resolver

  1. A sample is available in the SQL Server 2000 sample files. Download the sql2000samples.cab from Updated Samples for SQL Server 2000 Service Pack 3. This downloads 8 files amounting to 6.9 MB.

  2. Extract the files from downloaded compressed .cab file.

  3. Run setup.exe

    Note Note

    When choosing the installation options, it is only necessary to install the Replication samples. (The default installation path is C:\Program Files (x86)\Microsoft SQL Server 2000 Samples\1033\)

  4. Go to installation folder. (The default folder is C:\Program Files (x86)\Microsoft SQL Server 2000 Samples\1033\sqlrepl\unzip_sqlreplSP3.exe)

  5. Run the unzip_sqlreplSP3.exe program.

    Note Note

    The sample com resolver will install (by default) to the C:\Program Files (x86)\Microsoft SQL Server 2000 Samples\1033\sqlrepl\resolver\subspres folder.

  6. In the subspres folder, find all occurrences of #include sqlres.h in all of the source files and replace them with #import "replrec.dll" no_namespace, raw_interfaces_only

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