Zero-Loss Continuous Replication with Performance Boost

Transaction replication is the only guaranteed method against potential data losses. Transaction replication is difficult and costly. Up-scaling of SQL Server performance is also difficult if real transactions (not only for BI) are involved.

PCTI's breakthrough synchronous parallel transaction engine was designed to address both problems.

Dynamic Serialization and Load Balancing

Dynamic serialization solves the replication performance problems. There are two crucial aspects: In-Flight Transaction Serialization for replication consistency with minimal overheads and In-Flight Transaction Load Balancing for scalable performance.

Using this technology, concurrent update transactions are dynamically serialized, read-only queries are automatically load balanced when passing through DB^x™ gateway. This ensures replication data consistency by enforcing the exact commit orders of serialized transactions on multiple standalone SQL Servers. Concurrent read-only queries are distributed to individual SQL Servers to boost performance.

Here are the specific rules for dynamic serialization:

1. INSERT (concurrent INSERTs are serialized only if insertion order is important)
2. DELETE (concurrent DELETEs are serialized only if deletion order is important)
3. UPDATE (concurrent UPDATEs are serialized only if they update the same row)
4. SELECT are load balanced across all target SQL Servers. The use of more SQL Servers in the cluster improves the performance. Load balancer's heuristics automatically takes care of load sharing via WAN connected SQL Servers.

Since most transactions are read-only and most concurrent updates do not need serialization, higher performance and higher availability can be achieved at the same time.

High Performance Synchronous Transaction Replication

Traditional two-phase-commit (2PC) protocol requires sequential transaction applications and immediate rollback if any error occurs. This design has negative impact on both transaction performance and availability.

PCTI introduces 2PC with parallel transaction application and non-stop batch resynchronization. Transactions are applied to multiple SQL Servers in parallel. Servers with inconsistent and inferior results are disconnected from the cluster. They must go through the non-stop batch resynchronization process before resuming service. This technology ensures consistent datasets on all replication targets at all times.

This technology allows continuous protection with zero transaction loss regardless of SQL Server and DB^x™ gateway failures. It allows dynamic expansion and contraction of a SQL Server cluster without extended service downtimes; any SQL Server can be taken offline for repair or service pack application with little impact on service availability. New servers can also be added when the need arises.