# Limitations of data type mapping in the AWS Schema Conversion Tool
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The following limitations apply when converting schemas using multiple servers in a single AWS SCT project:
+ You can add the same server to a project only once.
+ You can't map server schemas to a specific target schema, only to a target server. AWS SCT creates the target schema during conversion.
+ You can't map lower-level source objects to the target server.
+ You can map one source schema to only one target server in a project.
+ Make sure to map a source to a target server to create an assessment report, convert schemas, or extract data.