Logon failed due to trigger execution

 The error "Logon failed due to trigger execution" occurs when a logon trigger in SQL Server prevents a user from logging in. Logon triggers are special stored procedures that execute in response to a LOGON event, and they can be used to enforce security policies, restrict access, or log login activity.

Steps to Resolve the Issue

1. Identify the Logon Trigger:

• Determine which logon trigger is causing the issue by querying the system catalog.

SELECT name, create_date, modify_date, is_disabled
FROM sys.server_triggers
WHERE type = 'TR' AND parent_class_desc = 'SERVER';

Check the Trigger Definition:

• Check the code of the logon trigger to understand its logic and why it might be causing the logon to fail.

-- Check the trigger defination
EXEC sp_helptext 'TriggerName';

Disable the Trigger (If Appropriate):

• If the trigger is incorrectly preventing logons, you can disable it.

-- Disable the trigger
DISABLE TRIGGER TriggerName ON ALL SERVER;

Fix the Trigger Logic (If Needed):

• If the trigger logic needs adjustment, modify the trigger code accordingly.

ALTER TRIGGER TriggerName ON ALL SERVER
FOR LOGON
AS
BEGIN
    -- Your trigger logic here
END;

Re-enable the Trigger:

• After fixing the issue, re-enable the trigger.

ENABLE TRIGGER TriggerName ON ALL SERVER;

Example Scenario and Solutions

Scenario: A Logon Trigger Prevents All Logins

Problematic Trigger:

CREATE TRIGGER PreventLogons
ON ALL SERVER
FOR LOGON
AS
BEGIN
    ROLLBACK;
END;

This trigger prevents all logons by rolling back every login attempt.

Solution:

1. Disable the Trigger:

DISABLE TRIGGER PreventLogons ON ALL SERVER;

Modify the Trigger Logic (e.g., to allow logins during business hours):

ALTER TRIGGER PreventLogons ON ALL SERVER
FOR LOGON
AS
BEGIN
    IF DATEPART(HOUR, GETDATE()) NOT BETWEEN 9 AND 17
    BEGIN
        ROLLBACK;
    END;
END;

Re-enable the Trigger:

ENABLE TRIGGER PreventLogons ON ALL SERVER;

Practical Steps to Diagnose and Fix the Issue

1. Identify Active Logon Triggers:

SELECT name, create_date, modify_date, is_disabled
FROM sys.server_triggers
WHERE type = 'TR' AND parent_class_desc = 'SERVER';

Review Trigger Definition:

-- Replace 'TriggerName' with the name of the trigger
EXEC sp_helptext 'TriggerName';

Disable the Trigger:

-- Replace 'TriggerName' with the name of the trigger
DISABLE TRIGGER TriggerName ON ALL SERVER;

Fix or Adjust the Trigger Logic:

ALTER TRIGGER TriggerName ON ALL SERVER
FOR LOGON
AS
BEGIN
    -- Adjust the logic to prevent inappropriate logon failures
END;

Re-enable the Trigger:

ENABLE TRIGGER TriggerName ON ALL SERVER;

By following these steps, you can diagnose and resolve issues related to logon triggers preventing successful logins