The restrictions associated with Oracle support of JSON data in Oracle Database are listed here.
Unless otherwise specified, an error is raised if a specified limitation is not respected.
General
Number of nesting levels for a JSON object or array: 1000, maximum.
JSON field name length: 32767 bytes, maximum.
SQL/JSON functions
Return-value length: 32767 bytes, maximum.
Path length: 4K bytes, maximum.
Number of path steps: 65535, maximum.
Simplified JSON syntax
Path length: 4K bytes, maximum.
Path component length: 128 bytes, maximum.
JSON search index
Field name length: 64 bytes, maximum. If a document has a field name longer than 64 bytes, it might not be completely indexed, and in that case an error is recorded in database view CTX_USER_INDEX_ERRORS.
JSON data guide
Path length: 4000 bytes, maximum. A path longer than 4000 bytes is ignored by a data guide.
Number of children under a parent node: 65535, maximum. A node that has more than 65535 children is ignored by a data guide.
Field value length: 32767 bytes. If a JSON field has a value longer than 32767 bytes then the data guide reports the length as 32767.
Zero-length field name: A zero-length (empty) object field name ("") is not supported for use with JSON data guide. Data-guide behavior is undefined for JSON data that contains such a name.
OSON
Field name length: 255 bytes, maximum.
No duplicate fields: If a JSON object with duplicate field names is represented using OSON then only one of these fields is present (kept).
No offload of HDFS external-table LOB data to Oracle Big Data SQL
JSON data that is stored in an external table that is based on Hadoop Distributed File System (HDFS) is not offloaded to Oracle Big Data SQL when LOB storage is used. See Oracle Big Data Appliance Software User's Guide
You cannot query JSON data across multiple shards unless it is stored as VARCHAR2.