Information About SQL Deadlocks

An “SQL Deadlock” occurs in Microsoft Dynamics 365 Business Central when two or more processes are waiting for resources that are locked by each other. In this situation, none of the involved transactions can proceed because each one is holding a resource the other needs. To resolve the conflict, the SQL server automatically selects one process as the deadlock victim and terminates it by rolling back the transaction. The other process then is able to continue the required changes.

Impact of SQL Deadlocks

• Data loss does not occur, as well-designed Dynamics AL code and their resdulting SQL transactions are designed to roll back cleanly in the event of failure.
• For end users, for example when using the Web Client, a deadlock will result in an error message. The user must then repeat the action.

Avoiding Deadlocks

• A consistent locking order across processes can prevent most deadlocks. This must be defined and enforced in the application logic.
• Complete avoidance is not always feasible, especially when performance considerations require varying lock sequences.

Relevance for the Anvaigo Mobile App

• SQL deadlocks are not critical in the Anvaigo Mobile App as automatic retry mechanisms ensure that failed transactions are reprocessed.
• The deadlock victim has no negative impact on data processing or the user experience as the user will not see any retries.
• A deadlock cannot always be prevented in this context, as the lock order of resources alone determines whether a deadlock situation occurs.
• However, this is not problematic because the system automatically retries the processing of incoming data, ensuring it is completed successfully.