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Adding a new record is usually a straightforward process and does not require a serializer version update. Given that an older version did not write this record and append-only nature of the WAL, we can simply add new record type and WAL will work out of the box. Changing record structure requires adding a new serializer version because we need to read both new and old record structure and write new record structure.

Compatibility Tests

TBDPDS compatibility tests framework is implemented in IgnitePersistenceCompatibilityAbstractTest which has several subclasses. General approach for such tests is to produce some PDS state on an older version and then check that a newer Ignite versions can be started using this state.