Migrating Logins from One SQL Server to Another

By
using the sp_help_revlogin SP, you can move logins from one server, and create
the login entries in the new server and retain the sid. By making sure that all
logins exist on the new server prior to copying a database, you will ensure there
will be no orphan users after you complete the database copy The sp_help_revlogin
SP helps DBA’s quickly move logins from
one server to another.

How
the sp_help_revlogin Works

The
process of moving logins requires not only the sp_help_revlogin SP, but also
the sp_hexidecimal SP. These scripts and more information about migrating
logons can be found in the following Microsoft Knowledge Base article http://support.microsoft.com/default.aspx?scid=kb;en-us;246133.
I have also included a script to create both of these SP’s at the bottom of this article. Let’s review the sp_help_revlogin process.

The
easiest way to execute the sp_help_revlogin script is via Query Analyzer. The
SP accepts a single optional parameter, @login_name. If you only want to
generate a single login, then you can pass a valid login to sp_help_revlogin,
and it will generate a script to create the specified login. When @login_name
is not specified this SP generates a TSQL script to create all the logins on
the server.

Based
on whether the @login_name was specified, the sp_help_revlogin SP builds a
cursor called login_curs that contains information in the sysxlogins table in
the master database for a single login or all the logins on the server, except sa’. The
columns placed in the cursor are sid, name, xstatus and password. The xstatus
column will be used to determine if the login is a Windows or SQL Server
Authenticated users, as well as whether the login has been denied access. The sid
and password will be used to make sure the new login on the new server retains
the same sid and password as the original server.

Next
the sp_help_revlogin SP processes through the login_curs cursor one login at a
time in a while loop. Inside the while loop the SP determines if the login is
a Windows authenticated user or group (xstatus = 4) or not. If the user is a
Windows authenticated user then a sp_grantlogin statement is generated. For
the SQL Server authenticated users a sp_addlogin statement, with the skip_encryption
parameter is generated. The skip_encryption parameter is used on the
sp_addlogin statement to tell SQL Sever that an encrypted password is being
specified when the login is being created, so the password should not be
encryted.

For
SQL Server authenticated users, the SP needs to determine the sid and password
of the login. Since the sid and the password as stored as binary numbers, the sid
and password values need to be converted to a string that contains the hexadecimal
representation of the binary number. The sp_hexadecimal SP is used to do this
binary number to hex string conversion.

When
the sp_help_revlogin execution is complete, the script to create the logins
should be displayed in the Query Analyzer results pane. All you need to do to
add these logins to a server would be just to copy the script from the results
pane and run it against the new server where you want to add the logins.

Other
uses for the sp_help_revlogin SP

Using
the sp_help_revlogin as it comes from Microsoft will move all logins or a
single login. Maybe you only want move all the logins for a single database.
It is easy to modify the code that creates the “login_curs” to identify only
the users you want to move.

Often
I am only moving a single database. When I do that, I modify the creation of
the “login_curs” cursor command to look like so:

    SELECT sid, name, xstatus, password FROM master..sysxlogins a join

    Your_DB..sysusers b on a.sid = b.sid

    WHERE srvid IS NULL AND name <> ‘sa’

By
using this logic instead, the sp_help_revlogin will only generate
sp_grantlogin, and sp_addlogins for users of the database Your_DB.

Another
possible use might be to generate the script for all logins, then delete the
logins you do not want to move. This method allows you to be selective in the
logins that will be created on the new server.

Conclusion

Here I have shown you a method to quickly generate a script that will move all
logins from one server to other, as well as offered you ideas on how to move a
sub set of users. I am sure you can find other uses for this sp. Using
sp_help_revlogin is much easier than re-entering all logins on a new server. In
addition, re-entering logins would most likely establish a new password for
each login moved, where as this sp allows you to move the passwords. Moving
the passwords from one server to another is more user friendly. SQL Server
users will be grateful that they do not have to remember a new password, and it
makes the migration a little more transparent to the SQL Server users.

Script to Create
sp_hexidecimal and sp_help_revlogin

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See All Articles by Columnist Gregory A. Larsen