External Table and Direct path load

Question

Hi,
I was just playing with Oracle sql loader and external table features. few things which i ovserved are that data loading through direct path method of sqlloader is much faster and takes much less hard disk space than what external table method takes. here are my stats which i found while data loading:
For Direct Path: -
# OF RECORDS.............TIME...................SOURCE FILE SIZE...................DATAFILE SIZE(.dbf)
478849..........................00:00:43.53...................108,638 KB...................142,088 KB
957697..........................00:01:08.81...................217,365 KB...................258,568 KB
1915393..........................00:02:54.43...................434,729 KB...................509,448 KB
For External Table: -
# OF RECORDS..........TIME...................SOURCE FILE SIZE...................DATAFILE SIZE(.dbf)
478849..........................00:02:51.03...................108,638 KB...................966,408 KB
957697..........................00:08:05.32...................217,365 KB...................1,930,248 KB
1915393..........................00:17:16.31...................434,729 KB...................3,860,488 KB
1915393..........................00:23:17.05...................434,729 KB...................3,927,048 KB
(With PARALLEL)
i used same files for testing and all other conditions are similar also. In my case datafile is autoextendable, hence, as par requirement its size is automatically increased and hard disk space is reduced thus.The issue is that, is this an expected behaviour? and why in case of external tables such a large hard disk space is used when compared to direct path method? Performance of external table load is also very bad when compared to direct path load.
one more thing is that while using external table load with PARALLEL option, ideally, it should take less time. But what i actually get is more than what the time was without PARALLEL option.
In both the cases i am loading data from the same file to the same table (once using direct path and once using external table). before every fresh loading i truncate my internal table into which data was loaded.
any views??
Deep
Message was edited by:
Deep

Answer 1

Thanx to all for your suggestions.
John, my scripts are as follows:
for external table:
CREATE TABLE LOG_TBL_LOAD
(COL1 CHAR(20),     COL2 CHAR(2),     COL3 CHAR(20),     COL4 CHAR(400),
     COL5 CHAR(20),     COL6 CHAR(400),     COL7 CHAR(20),     COL8 CHAR(20),
     COL9 CHAR(400),     COL10 CHAR(400))
ORGANIZATION EXTERNAL
(TYPE ORACLE_LOADER
DEFAULT DIRECTORY EXT_TAB_DIR
ACCESS PARAMETERS
(RECORDS DELIMITED BY NEWLINE
FIELDS TERMINATED BY WHITESPACE OPTIONALLY ENCLOSED BY '"' MISSING FIELD VALUES ARE NULL     
LOCATION ('LOGZ3.DAT')
REJECT LIMIT 10;
for loading i did:
INSERT INTO LOG_TBL (COL1, COL2, COL3, COL4,COL5, COL6,
COL7, COL8, COL9, COL10)
(SELECT COL1, COL2, COL3, COL4, COL5, COL6, COL7, COL8,
COL9, COL10 FROM LOG_TBL_load_1);
for direct path my control file is like this:
OPTIONS (
DIRECT = TRUE
LOAD DATA
INFILE 'F:\DATAFILES\LOGZ3.DAT' "str '\n'"
INTO TABLE LOG_TBL
APPEND
FIELDS TERMINATED BY WHITESPACE OPTIONALLY ENCLOSED BY '"'
(COL1 CHAR(20),
COL2 CHAR(2),
COL3 CHAR(20),
COL4 CHAR(400),
COL5 CHAR(20),
COL6 CHAR(400),
COL7 CHAR(20),
COL8 CHAR(20),
COL9 CHAR(400),
COL10 CHAR(400))
and ya, i have used same table in both the situations. after loading once i used to truncate my table, LOG_TBL. i used the same source file, LOGZ3.DAT.
my tablespace USERS is loaclly managed.
thanks