How Shadowbase DDL Command Replication Keeps Schema Changes and Data Replication in Sync

How Shadowbase DDL Command Replication Keeps Schema Changes and Data Replication in Sync

Shadowbase DDL Command Replication (SB DCR) for HPE Nonstop Software

Database replication depends on more than moving data. When file definitions, table structures, or other schema elements change, source and target systems must remain aligned or replication can fail. Shadowbase DDL Command Replication (DCR) addresses that challenge by capturing source DDL commands, mapping them to the target environment, and applying them in sequence with ongoing replication activity. This helps keep source and target schemas synchronized while supporting continued data replication.

Article highlights:

• DCR captures schema changes such as file/table creates, alters, and purges/drops, then applies them to the target database.
• In Enscribe and SQL/MP environments, source FUP and SQLCI commands can be replayed on the target.
• DDL replication is integrated with DML replication so schema changes are applied at the proper point in the replication stream.
• Proper sequencing helps reduce replication failures caused by schema mismatches between source and target systems.

How Shadowbase DCR Works

Shadowbase DDL Command Replication captures schema-related changes and propagates them to the target environment. Supported operations include file/table creation, file/table alteration, file/table purge/drop operations, other object definition changes, Enscribe file system DDL commands executed through FUP, and SQL/MP SQLCI DDL commands. Mapping capabilities ensure the commands are directed to the correct target objects.

By integrating DDL replication with DML replication, Shadowbase applies schema changes at the correct point in the replication stream. This keeps source and target structures aligned and helps reduce the risk of replication interruptions that can occur when data changes arrive before the corresponding schema update.

Why Sequencing Matters

Schema changes and data changes must remain synchronized. Shadowbase integrates DDL and DML replication so that a file or table can be altered while replication remains active, provided the DDL is propagated and replayed in the proper order before dependent DML reaches the target system.

Without that coordination, replication updates can fail because the expected schema is missing or out of date. The resulting inconsistencies can create operational challenges and increase the risk of data loss. Shadowbase is designed to eliminate that failure window by maintaining the correct ordering of schema and data changes.

Practical Example

Consider a replicated table that requires a new column. The recommended process is to issue the ALTER TABLE command on the source system, allow Shadowbase to propagate and apply the DDL to the target, and then enable application functionality that depends on the new column. If rows referencing the new column reach the target before the schema update has been applied, replication can fail or the data can be treated as an error. DCR maintains the required sequence automatically, removing the need to stop replication and manually update schemas.

Best Practices

For replicated environments, schema modifications should be performed through Shadowbase DDL replication rather than by managing source and target schemas independently. Keeping DDL changes within the replication stream helps reduce the risk of structural inconsistencies that can affect DML replication.

In mixed-platform environments, organizations should maintain clear mappings for object names and structural translations. Schema changes and replay sequencing should also be tested and validated in a test or certification environment before being deployed into production.

Supporting Broader Schema Management

Shadowbase also provides related utilities that support schema-management workflows. The Shadowbase Data Definition Language Utility (SBDDLUTL) and the Shadowbase SQL/MP Schema Conversion Utility (SBCREATP) can be used to convert and map source definitions into target SQL equivalents.

Wrap up

Shadowbase DDL Command Replication helps keep replicated environments synchronized by capturing, sequencing, and applying schema changes alongside ongoing DML replication. By ensuring that structural changes are applied before dependent data updates reach the target, Shadowbase DCR enables organizations to implement schema modifications without interrupting replication or manually coordinating source and target updates. The result is a more resilient replication environment, lower operational risk, and greater confidence that critical data remains protected and available as systems evolve.

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