I was trying to set up database mirroring in my freshly created Azure Virtual Machines and encountered an error. The error was talking about the connectivity problem, but it was something else. Let us learn about how to fix the database mirroring connection error 4.
Environment SRV_P -Principal- Microsoft SQL Server 2014 12.0.4422.0 (X64) SRV_M-Mirror- Microsoft SQL Server 2014 12.0.4422.0 (X64) SRV_W-witness- SQL SERVER 2008 R2 SYMPTOMS
As soon as I configure database mirroring and click on “Start Mirroring”, I was getting below error.
Alter failed for Database ‘SQLAUTHORITY’. (Microsoft.SqlServer.Smo)An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)
The ALTER DATABASE command could not be sent to the remote server instance ‘TCP://SRV_W.SQLAUTHORITY.net:5022’. The database mirroring configuration was not changed. Verify that the server is connected, and try again. (Microsoft SQL Server, Error: 1456)
I looked around in ERRORLOG files to see if there is anything interesting.
PRINCIPAL SERVER 2016-12-26 01:23:16.710 spid43s Database mirroring connection error 4 ‘An error occurred while receiving data: ’24(The program issued a command but the command length is incorrect.)’.’ for ‘TCP://SRV_W.sqlauthority.net:5022’.2016-12-26 01:23:36.490 spid75 Error: 1456, Severity: 16, State: 3.
2016-12-26 01:23:36.490 spid75 The ALTER DATABASE command could not be sent to the remote server instance ‘TCP://SRV_W.sqlauthority.net:5022’. The database mirroring configuration was not changed. Verify that the server is connected, and try again.
2016-12-26 01:23:36.750 spid41s Database mirroring is active with database ‘SQLAUTH’ as the principal copy. This is an informational message only. No user action is required.
MIRROR 2016-01-01 22:28:14.370 Logon Database Mirroring login attempt by user ‘SQLAUTHORITY\SRV_P$.’ failed with error: ‘Connection handshake failed. The login ‘SQLAUTHORITY\SRV_P$’ does not have CONNECT permission on the endpoint. State 84.’. [CLIENT: 10.0.40.34] WORKAROUND/SOLUTION
I realized that this is a typical issue where service account is set to LocalSystem. Due to this mirroring, would use the machine name (having $ symbols at the end) to communicate. There are two workarounds for this.
Change the Service account to domain account
Read more here: SQL SERVER Best Practices About SQL Server Service Account and Password Management
If you don’t want to use domain account, then we need to create machine account as login and provide CONNECT permission to endpoint (as mentioned in error message)On principal
use [master] GO CREATE LOGIN [SQLAUTHORITY\SRV_M$] FROM windows GO GRANT CONNECT ON ENDPOINT::[Mirroring] TO [SQLAUTHORITY\SRV_M$] GO use [master] GO CREATE LOGIN [SQLAUTHORITY\SRV_W$] FROM WINDOWS GO GRANT CONNECT ON ENDPOINT::[Mirroring] TO [SQLAUTHORITY\SRV_W$]Notice that we are giving permission to machine account of mirror and witness. Same set of command to be run on Mirror and Witness as well with other two machines account.
On Mirror = SQLAUTHORITY\SRV_W$ and SQLAUTHORITY\SRV_P$
On Witness = SQLAUTHORITY\SRV_P$ and SQLAUTHORITY\SRV_M$
Same issue can happen in AlwaysOn availability group as well if account is set to LocalSystem.
Have you encountered such errors? What was the solution?
Reference: Pinal Dave ( https://blog.sqlauthority.com )