How to solve ORA-55622 during DROP USER ... CASCADE;

During a DROP USER ... CASCADE operation, you may encounter the following error:

ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-55622: DML, ALTER and CREATE UNIQUE INDEX operations are not allowed on table "SCOTT"."SYS_FBA_TCRV_83287"

Solution: disable flashback archive:

Check the currently enabled flashback archive tables:

set lines 155
col TABLE_NAME for a30
col OWNER_NAME for a30
col FLASHBACK_ARCHIVE_NAME for a30
col ARCHIVE_TABLE_NAME for a30
col STATUS for a30
SELECT * 
FROM DBA_FLASHBACK_ARCHIVE_TABLES 
WHERE OWNER_NAME=upper('SCOTT');

Put the following in a script called gen_disable_fda.sql:

set trimspool on
set heading off
set feedback off
set echo off
set verify off
spool disable_flb_archive.sql
SELECT 'spool disable_flb_archive.log' FROM dual;
SELECT 'alter table ' || owner_name || '.' || table_name || ' no flashback archive;' 
FROM DBA_FLASHBACK_ARCHIVE_TABLES 
WHERE OWNER_NAME=upper('SCOTT');
SELECT 'exit' FROM dual;
exit

The script above will generate alter table statements for all SCOTT-owned tables with flashback archive enabled:

sqlplus / as sysdba @gen_disable_fda.sql

Finally, run the script disable_flb_archive.sql, which now contain statements as shown below:

alter table SCOTT.EMP no flashback archive;

After this has been done, the schema may be dropped.