Exclusive lock mode in a partitioned table

Hello experts,

                       I am compressing one of the biggest partitioned table using HCC with archive high.First I am generating .sql file like below and then running .sql script to apply compression.

'ALTER TABLE ITRONADM.READING MOVE SUBPARTITION '|| SUBPARTITION_NAME ||' COMPRESS FOR ARCHIVE HIGH UPDATE INDEXES;' from dba_tab_subpartitions where table_name='READING'

compression='DISABLED' ;

While compression is going on I can see table level exclusive mode lock is created.

SQL> select a.object_id,a.locked_mode,b.object_name from v$locked_object a,dba_objects b where a.object_id=b.object_id

OBJECT_ID LOCKED_MODE OBJECT_NAME