PDF's storing in Compressed BLOB Securefile doesn't save space

Question

Hello 1 have a Test-table in 10G with 1 LOB-segment of 1700 Mb , 1743 records with PDF's
In 11G 11.1.0.7 i create a table with SCEUREFILE in ASSM tablespace, the table is partitioned.
When 1 insert the 1743 records wioth PDF's the total segmentsize is even 1900 MB...???
Why are my PDF's not more compressed?
CREATE TABLE SNL_SCAN.DOCUMENTEN_LGE
OWNER VARCHAR2(50 BYTE),
COMPANY VARCHAR2(50 BYTE),
SCAN_ID VARCHAR2(50 BYTE) NOT NULL,
DOCUMENT BLOB,
FILENAME VARCHAR2(255 BYTE),
CONTENT_TYPE VARCHAR2(50 BYTE),
ORDER_DATE DATE,
SCAN_DATE DATE,
STATUS VARCHAR2(1 BYTE),
CUSTOM_01 VARCHAR2(50 BYTE),
CUSTOM_02 VARCHAR2(50 BYTE),
CUSTOM_03 VARCHAR2(50 BYTE),
CUSTOM_04 VARCHAR2(50 BYTE),
CUSTOM_05 VARCHAR2(50 BYTE),
CUSTOM_06 VARCHAR2(50 BYTE),
OWNER_ID NUMBER(9) NOT NULL,
SCAN_PLACE_DATE DATE DEFAULT sysdate
TABLESPACE SCAN_DATA
PCTUSED 0
PCTFREE 10
INITRANS 1
MAXTRANS 255
PARTITION BY RANGE (SCAN_DATE)
INTERVAL( NUMTOYMINTERVAL(1,'MONTH'))
PARTITION DOCUMENTEN_LGE_200605 VALUES LESS THAN (TO_DATE(' 2006-06-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
LOGGING
COMPRESS FOR ALL OPERATIONS
TABLESPACE SCAN_DATA
LOB (DOCUMENT) STORE AS SECUREFILE
( TABLESPACE SCAN_DATA
ENABLE STORAGE IN ROW
CHUNK 8192
RETENTION
NOCACHE
COMPRESS HIGH
STORAGE (
INITIAL 64K
NEXT 1M
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0
FREELISTS 1
FREELIST GROUPS 1
BUFFER_POOL DEFAULT
PCTFREE 10
INITRANS 1
MAXTRANS 255
STORAGE (
INITIAL 64K
NEXT 1M
MINEXTENTS 1
MAXEXTENTS UNLIMITED
BUFFER_POOL DEFAULT
COMPRESS FOR ALL OPERATIONS
NOCACHE
NOPARALLEL
MONITORING
ENABLE ROW MOVEMENT;

Answer 1

Hello Sushil,
i have used the securefileperformancepaper.pdf as test doument, i also simplefied the test:
1.
Inserted the pdf into a table:
declare
Dest_loc BLOB;
Src_loc BFILE;
BEGIN
INSERT INTO SNL_SCAN.DOCUMENTEN (scan_id,owner_id, document) VALUES (1,1, EMPTY_BLOB())
RETURNING document INTO Dest_loc;
Src_loc := BFILENAME ('DIR_TESTCASE', 'sec.pdf');
DBMS_LOB.FILEOPEN (Src_loc, DBMS_LOB.LOB_READONLY);
DBMS_LOB.LOADFROMFILE (Dest_loc, Src_loc, dbms_lob.getlength (Src_loc));
DBMS_LOB.FILECLOSE (Src_loc);
INSERT INTO SNL_SCAN.DOCUMENTEN (scan_id,owner_id, document) VALUES (2,2, EMPTY_BLOB())
RETURNING document INTO Dest_loc;
Src_loc := BFILENAME ('DIR_TESTCASE', 'sec.pdf');
DBMS_LOB.FILEOPEN (Src_loc, DBMS_LOB.LOB_READONLY);
DBMS_LOB.LOADFROMFILE (Dest_loc, Src_loc, dbms_lob.getlength (Src_loc));
DBMS_LOB.FILECLOSE (Src_loc);
END;
2.
created table
CREATE TABLE NOCOMP ( a BLOB)
LOB(a) STORE AS SECUREFILE
( CACHE ) ;
inserted 10 documents
10x-----
insert into nocomp
(select document from snl_scan.documenten where scan_id= '1');
commit;
the lobsegment is now 4,19 MB
3.
inserted another 100 rows
the lobsegment is now 42,2 MB
4.
Created table with compressed LOB
CREATE TABLE COMP ( a BLOB)
LOB(a) STORE AS SECUREFILE
( COMPRESS HIGH
CACHE ) ;
inserted 10 documents
10x-----
insert into comp
(select document from snl_scan.documenten where scan_id= '1');
commit;
the lobsegment is now 4,25 MB
inserted another 100 rows
the lobsegment is now 42,2 MB
5.
so there is no compression.
6.
Created table with compressed LOB an DEDUPLICTION
CREATE TABLE COMP_DEDUP ( a BLOB)
LOB(a) STORE AS SECUREFILE
( COMPRESS HIGH
DEDUPLICATE
CACHE ) ;
7,
inserted 10 documents
10x-----
insert into comp
(select document from snl_scan.documenten where scan_id= '1');
commit;
the lobsegment is now 1,25 MB
inserted another 100 rows
the lobsegment is now 1,25 MB
Deduplication is working, compression with the oracle pdf isn't saving any space......
8.
VIEW DBA_LOBS
TABLE_NAME     COL     SEGMENT_NAME CACHE LOGGING ENCRYPT     COMPRESSION DEDUPLICATION     IN_ROW     FORMAT     PARTITIONED     SECUREFILE
COMP_DEDUP     A     SYS_LOB0000107972C00001$$     YES     YES     NO     HIGH     LOB     YES N/A NO     YES
COMP      A     SYS_LOB0000107981C00001$$     YES     YES     NO     HIGH     NO     YES N/A NO     YES
NOCOMP      A     SYS_LOB0000107984C00001$$     YES     YES     NO     NO     NO     YES      N/A NO     YES
Hope this helps.
Rob Tousain
00 31 6 28660287