Transitioning from Oracle's relational model to Couchbase's JSON model involves careful consideration of data type mapping, as Oracle requires explicit declaration of column types, while Couchbase automatically interprets data types through JSON syntax. The conversion encompasses various data types, including strings, dates, booleans, numerics, binary data, and large objects, each with specific considerations for mapping. For instance, in Couchbase, string data is inherently Unicode with a maximum length of 20MB, and date and time are represented in ISO 8601 format as strings, offering extensive functions for formatting and arithmetic. Oracle's complex data types such as objects and arrays have built-in support in Couchbase's JSON model, allowing for nested levels and versatility in data representation. Additionally, the conversion from primary keys in Oracle to document keys in Couchbase requires careful handling to ensure uniqueness within a bucket, often by converting parts to strings and using separators.