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ERROR_DS_NONSAFE_SCHEMA_CHANGE
Schema safety checks protect existing instances from new contradictions
ERROR_DS_NONSAFE_SCHEMA_CHANGE rejects a modification whose effect is unsafe for objects that may already exist. Examples include adding a new mandatory attribute to an existing class, changing a class category, altering a constructed attribute, or modifying top in a way that introduces more than computed back-link attributes.
Model the effective class definition, including inherited and auxiliary classes, rather than reviewing only the field directly edited in LDIF. A new mustContain can invalidate millions of existing objects immediately because they lack the value. Prefer a new optional attribute, a new versioned class, or an auxiliary class that adds only optional data. Before deployment, enumerate existing instances and verify application behavior in a representative forest; schema replication makes a successful unsafe change difficult to contain once accepted.
Impact analysis before redesigning the extension
- Effective mandatory attributes before and after the change.
- Existing instances of every affected class.
- Auxiliary and superclass inheritance paths.
- Optional or versioned alternative design.
References
- MS-ADTS: schema update safety checks
- Microsoft: prohibited modifications to existing schema
- Microsoft: inherited class characteristics
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