# Schema management (Iceberg)
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+ Register schemas in AWS Glue Schema Registry before creating Channels. GSR is the source of truth; creation fails if the schema cannot be resolved.
+ For plain `JSON`, provide the GSR schema ARN that defines the data; for `JSON_SCHEMA_GSR`, the schema ID is embedded in each record.
+ **Schema evolution is not supported.** Avoid changing the schema after a Channel is created; if the schema must change, create a new Channel (and a new table).