I am going to introduce another new feature in Oracle Database 21c. Oracle Data Pump(DP) supports optional index compression on imports in this release, including for Oracle Autonomous Database. Oracle DP supports adding, changing, and eliminating table compression. Oracle Database 21c supports index compression as well by introducing a new TRANSFORM parameter clause, INDEX_COMPRESSION_CLAUSE. This clause enables you to control whether index compression is performed during import. Adding this clause also enables you to specify index compression on import with the autonomous services.

If  NONE is specified, then the index compression clause is omitted (and the index is given the default compression for the tablespace). However, if you use compression, then Oracle recommends that you use COMPRESS ADVANCED LOW Indexes are created with the specified compression.
If the index compression clause is more than one word, then it must be contained in single or double quotation marks. Also, your operating system can require you to enclose the clause in escape characters, such as the backslash character. For example:


Determining this parameter changes the type of compression for all indexes in the job. For more information see: https://docs.oracle.com/en/database/oracle/oracle-database/21/sutil/oracle-datapump-import-utility.html#GUID-64FB67BD-EB67-4F50-A4D2-5D34518E6BDB