Synchronous replication

As explained in 100 SQL Server Mistakes and How to Avoid Them

Synchronous replication propagates each data change to a secondary system and waits for its completion before completing the change on the primary.

Synchronous replication sends each write to a secondary system and waits for it to finish before completing the write on the primary. This prevents data loss during an unexpected failure, but network latency directly affects performance. section 13.1

Mistake: treating HA and DR as the same problem

Putting synchronous availability-group replicas in separate data centers may seem to provide both high availability and disaster recovery. Unless the sites have a very fast, low-latency connection, every cross-site write can slow the primary. Use synchronous replication where latency is acceptable; distinguish local automatic failover from cross-site disaster recovery. section 13.1

Figure 13.1 HA topology with availability groups providing automatic failover in a single site

A local availability-group topology makes synchronous replication’s automatic-failover role concrete. section 13.1

How 100 SQL Server Mistakes and How to Avoid Them covers it

How deep it goes

Explains write acknowledgment and latency consequences, but stops short of configuration or diagnostic procedures.

Examples

Uses local availability groups and geographically separated data centers to contrast automatic failover with latency-sensitive replication.

What you can do after

Evaluate whether synchronous replication fits a topology by weighing data-loss protection against network latency and write performance.

How it connects

Connects availability groups with high availability, disaster recovery, read scaling, network latency, and traditional clustering.

liveBookmanning.com

Read 100 SQL Server Mistakes and How to Avoid Them on liveBook Get the book at manning.com

Also explained in

• 

  liveBookmanning.com
  PostgreSQL Mistakes and How to Avoid ThemSynchronous replication requires configured replication standbys to confirm replicated changes before the committing transaction completes.

Compare how 2 books explain synchronous replication →

Related concepts

• replicationcontrasts with · Replication is the creation or maintenance of multiple copies of data, state, or functionality across separate locations or components.
• replication lagcontrasts with · Replication lag is the elapsed delay between a change being applied or committed at a source and becoming applied or visible at a replication target.
• acknowledgmentuses · An acknowledgment is a protocol message or signal confirming that transmitted data, a message, request, or operation was received or processed.
• failoverproduces · Failover is the transfer of service or workload from a failed or unavailable component to a functioning alternate or standby component.
• uptimeimplements · Uptime is the duration or proportion of a specified period during which a system or service is operational and available to provide its intended function.

This explainer was generated by Manning's knowledge graph from the text of 100 SQL Server Mistakes and How to Avoid Them. The section links point to the parts of the book it draws on.