CDM is a method to replicate changes between multiple systems. When enabled, CDM replicates SQL changes that are non-deterministic and can produce different results if run in parallel on different systems. CDM sends a non-deterministic SQL to the active system and then captures all the resulting data changes. It then multicasts those data changes to the standby systems. This allows Business Continuity Manager to replicate changes that involve non-deterministic functions like RANDOM and SAMPLE and writes to tables that include IDENTITY columns.
- Identity Columns
- Dynamic SQL in Stored Procedures
- Non-deterministic ordering or sampling (that is, Sample, TOP, ROWNUMBER)
- Analytic functions
When non-deterministic objects or triggers are identified, Business Continuity Manager processes the action on the active Teradata system, then uses CDM to send and override the values on the standby system.