These errors typically occur when the client cannot reach the database endpoint or authentication fails.

Error 40613 – Database unavailable

Message: The database 'mydb' is not currently available.

Resolution:

1. Check the database's status in the Azure portal.
2. Verify that the firewall rules allow your client IP.
3. Ensure the logical server is not paused (serverless tier).

Login failed for user

Message: Login failed for user 'username'.

Resolution:

• Confirm the username and password.
• Make sure the user exists in the database.
• Review Azure AD authentication settings if using Azure AD.

Identify and mitigate latency, high CPU, and I/O bottlenecks.

Long‑running queries

SELECT * FROM dbo.LargeTable WHERE SomeColumn = 'Value'

Tips:

• Use EXPLAIN plans via sys.dm_exec_query_plan.
• Apply appropriate indexes.
• Consider partitioning large tables.

CPU throttling (DTU/vCore limits)

Monitor sys.resource_stats and scale up if necessary.

Azure SQL Database provides automated backups. Use Point‑In‑Time Restore (PITR) for recovery.

Restore failed with error 30113

Message: Restore operation failed. The backup does not exist.

Resolution:

1. Check the retention period for the database.
2. Ensure the target time is within the backup window.
3. Verify you have sufficient service tier resources for the restore.

Common security‑related issues and their fixes.

Firewall rule not allowing client IP

Message: Client with IP address X.X.X.X is not allowed to access the server.

Action:

• Navigate to Firewalls and virtual networks in the Azure portal.
• Add the client IP or a range that includes it.

Transparent Data Encryption (TDE) disabled

Ensure TDE is enabled for compliance:

ALTER DATABASE CURRENT SET ENCRYPTION ON;

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