SAP HANA -Types Of Replication Modes

  • Synchronous in-memory (default): The primary system commits the transaction after it receives a reply that the log was received by the secondary system, but before it has been persisted. The transaction delay in the primary system is shorter, because it only includes the data transmission time.
  • Synchronous with full sync option means that log write is successful when the log buffer has been written to the logfile of the primary and the secondary instance. In addition, when the secondary system is disconnected (for example, because of network failure) the primary systems suspends transaction processing until the connection to the secondary system is re-established. No data loss occurs in this scenario
  • Synchronous: The primary system does not commit a transaction until it receives confirmation that the log has been persisted in the secondary system. This mode guarantees immediate consistency between both systems, however, the transaction is delayed by the time it takes to transmit the data to and persist it in the secondary system.
  • Asynchronous: The primary system sends redo log buffers to the secondary system asynchronously. The primary system commits a transaction when it has been written to the log file of the primary system and sent to the secondary system through the network. It does not wait for confirmation from the secondary system.

    This option provides better performance because it is not necessary to wait for log I/O on the secondary system. Database consistency across all services on the secondary system is guaranteed. However, it is more vulnerable to data loss. Data changes may be lost on takeover.

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