Oracle-L: drop table vs truncate table -- performance

From: gmei <gmei_at_incyte.com>
Date: Mon, 10 Mar 2003 13:39:31 -0800
Message-ID: <F001.00565494.20030310133931@fatcity.com>

Hi:
Oracle 8173 on Sun Solaris 2.8.
I am running a program that creates and drops tables repeatedly in a schema. The table dropping part looks like this:

drop table ypd.t1 cascade constraints;
drop table ypd.t2 cascade constraints;
drop table ypd.t3 cascade constraints;
drop table ypd.t4 cascade constraints;

....

I thought I might be able to use "truncate table ..." and then "drop table ..." to make this process a bit faster. However the tests I did today showed otherwise:

SQL> select bytes from dba_segments where segment_name='SEQUENCE';

BYTES

1949810688

SQL> create table ypd_owner.SEQUENCE1
2 tablespace ypd nologging as select * from mt.SEQUENCE;

Table created.

Elapsed: 00:04:272.50
SQL> drop table ypd_owner.SEQUENCE1;

Table dropped.

Elapsed: 00:00:05.19
SQL> create table ypd_owner.SEQUENCE1
2 tablespace ypd nologging as select * from mt.SEQUENCE;

Table created.

Elapsed: 00:04:275.85
SQL> truncate table ypd_owner.SEQUENCE1;

Table truncated.

Elapsed: 00:00:06.99
SQL> drop table ypd_owner.SEQUENCE1;

Table dropped.

Elapsed: 00:00:00.70

Tablspace ypd is LMT. Similar test on smaller table showed the same result "drop table ..." is faster than "truncate table ...". Any explanation? TIA. Guang

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Author: gmei
INET: gmei_at_incyte.com

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