LOB Column segments grow all the time in Oracle 19c

Hello,

when having a table with BLOB or CLOB columns it seams that the related segment is growing all the time causing that the underlying tablespace aquires more disk space from the operating system. The traffic pattern for these effected columns is that quite many rows are inserted per day and all of them have JSON data stored in the BLOB column. After some retention period the old rows are deleted.

Now using DBMS_SPACE.SPACE_USAGE() it reveals that the value for Expired Blocks/Bytes grows very high. In a concrete case we stopped all DML and used a ALTER TABLE theowner.thetable MOVE LOB('LOBCOL') STORE AS (TABLESPACE theTS). This is quite a heave admin operation and requires the rebuild of indexes too.