Insert into .. select table_name----CLOB table very slow insert

Hi Experts,

I am facing below issue while running creating partition table with a non partition table.

Below are the details for the activity.

NOTE:

REFERENCE_INSTANCE -- ORIGINAL NON PARTITION TABLE.

In GB::

EAI_SOAINFRA                   REFERENCE_INSTANCE               TABLE                             103.708008

EAI_SOAINFRA                   SYS_LOB0000075987C00014$$        LOBSEGMENT                         241.97522  REFERENCE_INSTANCE

EAI_SOAINFRA                   SYS_LOB0000075987C00015$$        LOBSEGMENT                        924.013855  REFERENCE_INSTANCE

REFERENCE_INSTANCE_TP -- ENPTY PARTITION TABLE CREATED SAME AS REFERENCE_INSTANCE EXCEPT THE NAME DIFFERENCE AND PARTITION DETAILS.

CREATE TABLE "EAI_SOAINFRA"."REFERENCE_INSTANCE_TP"

   ( "ECID" VARCHAR2(100 BYTE),

  "ID" NUMBER(*,0),

  "COMPOSITE_INSTANCE_ID" NUMBER(*,0),

  "PARENT_ID" VARCHAR2(100 BYTE),

  "CONVERSATION_ID" VARCHAR2(100 BYTE),

  "COMPOSITE_DN" VARCHAR2(500 BYTE),