This post is part of a blog series.

In Data Guard, when Fast-Start Failover runs in Maximum Performance mode, the FSFP process tracks lag to keep the primary database within safe limits.
Traditionally, FSFP used APPLY LAG to measure lag, a legacy from older redo transport. But APPLY LAG may not reflect real data loss risk: TRANSPORT LAG shows how much data hasn’t reached the standby.
With 26ai, you can set FastStartFailoverLagType to APPLY (default) or TRANSPORT.
Consider switching this property to TRANSPORT to track real data loss exposure.

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Ludovico

Principal Product Manager at Oracle

Ludovico is a member of the Oracle Database High Availability (HA), Scalability & Maximum Availability Architecture (MAA) Product Management team in Oracle. He focuses on Oracle Data Guard, Flashback technologies, and Cloud MAA.

Latest posts by Ludovico (see all)

• Data Guard 26ai – #3: Choice of Lag Type for Fast-Start Failover - January 29, 2026
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