Logon triggers in SQL server
As the name implies Logon triggers fire in response to a LOGON event. Logon triggers fire after the authentication phase of logging in finishes, but before the user session is actually established.
Logon triggers can be used for
1. Tracking login activity
2. Restricting logins to SQL Server
3. Limiting the number of sessions for a specific login
Logon trigger example : The following trigger limits the maximum number of open connections for a user to 3.
CREATE TRIGGER tr_LogonAuditTriggers
ON ALL SERVER
FOR LOGON
AS
BEGIN
DECLARE @LoginName NVARCHAR(100)
Set @LoginName = ORIGINAL_LOGIN()
IF (SELECT COUNT(*) FROM sys.dm_exec_sessions
WHERE is_user_process = 1
AND original_login_name = @LoginName) > 3
BEGIN
Print ‘Fourth connection of ‘ + @LoginName + ‘ blocked’ ROLLBACK
END
END
An attempt to make a fourth connection, will be blocked.
