After a failover, the primary replica of the database is running on a different logical server, which has a different server name (endpoint). To restore connectivity, the application's connection string must be updated to point to the fully qualified domain name (FQDN) of the new primary server. While using a failover group listener automates this redirection, the question implies a manual step is needed, which is typical for active geo-replication scenarios without a failover group. The application must be redirected to the new endpoint to re-establish a connection.

A. Configure SalesSQLDb1 as writable.

The failover process automatically promotes the secondary replica to a read-write primary. This action is redundant and unnecessary.

C. Update the firewall rules of SalesSQLDb1.

Firewall rules, like logins, should be configured on the secondary server before a failover occurs to ensure a smooth transition and minimize downtime.

D. Update the users in SalesSQLDb1.

Contained database users are replicated with the database. Server-level logins must be configured on the secondary server before the failover to prevent authentication failures.

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1. Microsoft Docs: Active geo-replication - Azure SQL Database.

Section: Managing application upgrades and failover

Quote: "If you are using active geo-replication to build a business continuity solution

you should verify that... The application is ready for failover. ... After failover

you must ensure that the connection string of your application is updated to connect to the new primary." This directly supports that updating the connection string is a required post-failover action.

2. Microsoft Docs: Configure a failover group for Azure SQL Database.

Section: Failover (planned)

Quote: "When your application is ready

you can initiate a failover. ... The failover group read-write listener is redirected to the new primary." This explains the automated alternative

but if not used

the connection string pointing to the old server FQDN would need manual updating

reinforcing the principle behind answer B.

3. Microsoft Docs: Business continuity overview with Azure SQL Database.

Section: Recover a database to the existing server

Quote: "To ensure full access to the new primary database... after failover

you must ensure that the appropriate security configuration (such as server-level firewall rules... and SQL logins and permissions) is in place for the target secondary server and contained in the master database." This confirms that firewall rules (C) and logins (related to D) are pre-failover configuration requirements

not post-failover recovery steps.