After starting the SAP HANA database, what action does the system take to ensure it is in a consistent mode?

The correct answer highlights a crucial aspect of maintaining database integrity and ensuring that the system recovers to a consistent state after a shutdown. When the SAP HANA database starts up, it must handle any transactions that were in progress at the time the database was stopped. If there are write transactions that were open, these could lead to inconsistencies in the data if not properly managed. Therefore, the system rolls back these open write transactions to ensure that the database resumes operation in a consistent state, effectively discarding any incomplete changes that could compromise data integrity.

Ensuring consistency is vital in database management, particularly in high-performance environments like SAP HANA. By rolling back any open write transactions, the system guarantees that only fully completed transactions are reflected in the database, maintaining the accuracy and reliability of the data.

The other options, while related to database operations, do not specifically address the need for consistency upon restarting from a stopped state. Completing all pending transactions could introduce inconsistencies if they were not committed before the shutdown, clearing all buffers pertains to memory management rather than transaction consistency, and restarting all services does not directly influence the state of transactions that were left open before the system was stopped.