GT.M database replication ensures that the primary and secondary system databases are logically identical, excluding latency in replication to the secondary system. During rolling upgrades, the primary and secondary will be logically equivalent but the exact values of M global variables may differ.
All database updates to replicated regions must occur only on the primary system.
GT.M will replicate all changes to the database on the primary system to the database on the secondary system.
Logical dual-site operation with GT.M requires a procedure for a number of situations, including both normal operation and failure scenarios.
Although logical dual-site applications based on database replication can operate manually, the requirements are complex enough to warrant automation via scripting. It is essential to design, implement, and test the procedures carefully to provide an automatic failover to the secondary system within seconds. GT.M provides the required functionality to implement continuous availability via logical dual-site; however, a considerable amount of system engineering is required to implement it.