Studio failed to connect to database with error Id:XDDS:9B560459.

Instructions

Step1.Check the event log of SQL server, because large transaction log may cause such error message. If transaction log is full, try to shrink transaction log

• For only one database environment, use the method in this article to shrink transaction log: CTX126916 - XenDesktop Database Transaction Log Growing Excessively.
• For Mirror or AlwayOn database environment:

1. Use BACKUP LOG [databasename] to disk = 'nul'. For reference please turn to http://www.cnblogs.com/TeyGao/p/3519954.html or http://realit1.blogspot.com/2016/02/shrinking-database-log-files-in.html.  This method may take a lot of time depending on the size of the log , so please be patient
2. Break the mirror configuration to shrink the transaction log quickly. This method may have a higher risk, since we make too many changes to the environment and Citrix has no professional database support to deal with anything urgent caused by such big changes.

Remove mirror from the primary SQL Server

Modify the recovery model to simple

Right click the database and shrink the transaction log

Backup the database and transaction log, copy them to Mirror database server 

Restore the backup with NORECOVERY option on Mirror database server 

select the database and select mirror task on primary database server 

click Configure Security to start Mirroring wizard 

Select Yes on Witness server page

Step2: Try to restart SQL Server and DDC if possible
Step3: Use ODBC to connect to database to test if database can accept remote connection
Open ODBC on any windows system, Click Add and select SQL Server and click Finish to create a New Data Source to SQL Server.

Give a name of the Data Source and select the SQL server name you want to connect, then click Next > Next > Finish > Test Data Source. If the DB can accept remote connection, TESTS COMPLETED SUCCESSFULLY message is displayed.



Other troubleshooting steps including but not limited to checking the 1433 port of SQL Server and "Allow remote connection to this server configurations" Configuration of Database.