to reduce the size of the overall db space, we are deleting unused rows/data from our tables which occupies more memory. But even after deleting around half of the existing rows, the memory size didnot decrease but increase.

Before delete:

Rows in table: 1.8 crore records

Space occupied: 1.77GB

After Delete:

Rows in table: 1 crore records

Space occupied: 6.91GB

Space occupied is retrieved from "select segment_name,segment_type,(bytes/1073741824) as memory_in_gb from dba_segments"

is ther some other way to actually reduce the memory occupied by table. also why even after deleting rows the space occupied increased.

DDL:

CREATE TABLE table_1
(
TABLE_1_ID NUMBER(18) NOT NULL
, LAST_UPDATE_DATE TIMESTAMP(6) NOT NULL
, LAST_UPDATED_BY VARCHAR2(64) NOT NULL
, CREATION_DATE TIMESTAMP(6) NOT NULL
, CREATED_BY VARCHAR2(64) NOT NULL
, CONSTRAINT table_1_PK PRIMARY KEY
(
TABLE_1_ID
)
DISABLE
)
LOGGING
TABLESPACE "TABLESPACE_1"
PCTFREE 10
PCTUSED 60
INITRANS 1
STORAGE
(
INITIAL 131072
NEXT 131072
MINEXTENTS 1
MAXEXTENTS 2147483645
PCTINCREASE 0
FREELISTS 4
FREELIST GROUPS 32
BUFFER_POOL DEFAULT
);

COMMENT ON TABLE ..................

CREATE INDEX table_1_N1 ON table_1 (table_1_f_ID, DATE_1)
LOGGING
TABLESPACE ""Default""
PCTFREE 40
INITRANS 11
STORAGE
(
INITIAL 4096
NEXT 1
MINEXTENTS 1
MAXEXTENTS 2147483645
PCTINCREASE 0
FREELISTS 4
FREELIST GROUPS 32
BUFFER_POOL DEFAULT
);



CREATE UNIQUE INDEX table_1_U1 ON table_1 (table_1_ID)
TABLESPACE ""Default""
STORAGE
(
BUFFER_POOL DEFAULT
);