Distributed Transaction Consistency in Oracle RAC Clusters

Abstract

Oracle Real Application Clusters (RAC) enables multiple database instances to operate against a
shared data layer while maintaining a single, consistent transactional state. Ensuring distributed
transaction consistency across nodes requires coordinated cache fusion block transfers, lock state
arbitration, and synchronized commit visibility. This study examines how workload timing,
transaction locality, and session routing influence the stability of RAC’s consistency model. Results
show that contention and synchronization overhead emerge not primarily from SQL complexity, but
from the temporal alignment of concurrent transactions and cross-instance routing behavior.
Maintaining node-local execution paths, staggering commit events, and isolating read-heavy
workloads reduce global coordination pressure and improve throughput stability. These findings
emphasize that distributed consistency in RAC is best achieved through joint optimization of
application workflows and cluster-level coordination mechanisms, rather than relying solely on
database tuning.