[ @rmtsrvname = ] 'rmtsrvname'

Is the name of a linked server that the login mapping applies to. rmtsrvname is sysname, with no default.

[ @useself = ] 'TRUE' | 'FALSE' | 'NULL'

Determines whether to connect to rmtsrvname by impersonating local logins or explicitly submitting a login and password. The data type is varchar(8), with a default of TRUE.

A value of TRUE specifies that logins use their own credentials to connect to rmtsrvname, with the rmtuser and rmtpassword arguments being ignored. FALSE specifies that the rmtuser and rmtpassword arguments are used to connect to rmtsrvname for the specified locallogin. If rmtuser and rmtpassword are also set to NULL, no login or password is used to connect to the linked server.

[ @locallogin = ] 'locallogin'

Is a login on the local server. locallogin is sysname, with a default of NULL. NULL specifies that this entry applies to all local logins that connect to rmtsrvname. If not NULL, locallogin can be a SQL Server login or a Windows login. The Windows login must have been granted access to SQL Server either directly, or through its membership in a Windows group granted access.

[ @rmtuser = ] 'rmtuser'

Is the remote login used to connect to rmtsrvname when @useself is FALSE. When the remote server is an instance of SQL Server that does not use Windows Authentication, rmtuser is a SQL Server login. rmtuser is sysname, with a default of NULL.

[ @rmtpassword = ] 'rmtpassword'

Is the password associated with rmtuser. rmtpassword is sysname, with a default of NULL.

0 (success) or 1 (failure)

When a user logs on to the local server and executes a distributed query that accesses a table on the linked server, the local server must log on to the linked server on behalf of the user to access that table. Use sp_addlinkedsrvlogin to specify the login credentials that the local server uses to log on to the linked server.

A default mapping between all logins on the local server and remote logins on the linked server is automatically created by executing sp_addlinkedserver. The default mapping states that SQL Server uses the user credentials of the local login when connecting to the linked server on behalf of the login. This is equivalent to executing sp_addlinkedsrvlogin with @useself set to true for the linked server, without specifying a local user name. Use sp_addlinkedsrvlogin only to change the default mapping or to add new mappings for specific local logins. To delete the default mapping or any other mapping, use sp_droplinkedsrvlogin.

Instead of having to use sp_addlinkedsrvlogin to create a predetermined login mapping, SQL Server can automatically use the Windows security credentials (Windows login name and password) of a user issuing the query to connect to a linked server when all the following conditions exist:

• A user is connected to SQL Server by using Windows Authentication Mode.
  
• Security account delegation is available on the client and sending server.
  
• The provider supports Windows Authentication Mode; for example, SQL Server running on Windows.
  

Note:
Delegation does not have to be enabled for single-hop scenarios, but it is required for multiple-hop scenarios.

After the authentication has been performed by the linked server by using the mappings that are defined by executing sp_addlinkedsrvlogin on the local instance of SQL Server, the permissions on individual objects in the remote database are determined by the linked server, not the local server.

sp_addlinkedsrvlogin cannot be executed from within a user-defined transaction.

Requires ALTER ANY LOGIN permission on the server.

A. Connecting all local logins to the linked server by using their own user credentials

The following example creates a mapping to make sure that all logins to the local server connect through to the linked server Accounts by using their own user credentials.

EXEC sp_addlinkedsrvlogin 'Accounts'

Or

EXEC sp_addlinkedsrvlogin 'Accounts', 'true'

Note:
If there are explicit mappings created for individual logins, they take precedence over any global mappings that may exist for that linked server.

B. Connecting a specific login to the linked server by using different user credentials

The following example creates a mapping to make sure that the Windows user Domain\Mary connects through to the linked server Accounts by using the login MaryP and password d89q3w4u.

EXEC sp_addlinkedsrvlogin 'Accounts', 'false', 'Domain\Mary', 'MaryP', 'd89q3w4u'

Security Note:
This example does not use Windows Authentication. Passwords will be transmitted unencrypted. Passwords may be visible in data source definitions and scripts that are saved to disk, in backups, and in log files. Never use an administrator password in this kind of connection. Consult your network administrator for security guidance specific to your environment.

Reference

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