When a database is migrated to a new server, two fundamental configurations for any connecting application must be addressed. First, the application's connection string, which contains the server's address (hostname or IP), must be updated to point to the new location; this is the 'mapping' (D). Second, security principals, such as the service account's login and database user permissions, must be recreated or re-established on the new server instance, as server-level permissions are not always included in a database backup/restore migration (A). Failure in either of these steps is a primary cause of application connectivity failure after a database move.

B. This is an unsubstantiated assumption. The existence of a new reporting system would not inherently cause the existing one to fail; it would be a planned decommissioning.

C. Locked jobs are typically a symptom of a connection failure, not the root cause. The application cannot process jobs because it cannot connect to the database first.

E. This is a generic statement of the problem's symptom. The specific reasons why the server is not permitted are the lack of correct permissions (A) or a firewall block.

F. It is highly improbable that improved database performance would cause a complete application failure. Applications are designed to process data as it is received.

1. Microsoft. (2023). Post-migration validation and optimization guide. Microsoft Learn. In the "Post-migration steps" section

two key activities are highlighted: Remediate applications ("After you migrate the data to the target environment

you need all the applications that formerly consumed the source to start consuming the target. Accomplishing this will in some cases require changes to the applications

" which includes updating connection strings) and Security (verifying and re-establishing logins

roles

and permissions on the new server instance).

2. Oracle. (2021). Database Administrator's Guide

19c. F10897-16

Chapter 20

"Transporting Data". The post-transportation tasks implicitly require administrators to ensure client connectivity

which involves updating connection descriptors (e.g.

in tnsnames.ora) to point to the new database location and verifying that user accounts and privileges are correctly configured in the new environment.

3. Schwarz

T. (2018). PostgreSQL 10 Administration Cookbook. Packt Publishing. Chapter 10

"Migration and Upgrades

" Section: "Migrating data to a new major version." The post-migration checklist includes steps such as "Adjust authentication rules (pghba.conf)" and "Point your applications to the new server

" which directly correspond to managing permissions and updating location mapping.