Re: GTT Locks

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 3 Mar 2004 06:51:13 -0000
Message-ID: <01e501c400eb$f084b500$6702a8c0@Primary>

9.2.0.4:

SQL> create table gtt (n1 number);

Table created.

Elapsed: 00:00:00.00

SQL> select sid, username from v$session where user_name = 'TEST_USER';

SID USERNAME

---------- ------------------------------
        16 TEST_USER

1 row selected.

Elapsed: 00:00:00.00
SQL> select * from V$lock where sid = 16;

no rows selected

Elapsed: 00:00:00.00
SQL> insert into gtt values(1);

1 row created.

Elapsed: 00:00:00.00
SQL> select * from V$lock where sid = 16;

ADDR     KADDR           SID TY        ID1        ID2      LMODE    REQUEST
 CTIME      BLOCK

-------- -------- ---------- -- ---------- ---------- ---------- ---------- ------ ----------

67B84268 67B84374         16 TX     196647       7419          6          0
     0          0
67B4E074 67B4E088         16 TM      30492          0          3          0
     0          0

2 rows selected.

Object 30492 is the table definition for the GTT, so I'm not reproducing your result.

In passing - has anyone got a system with an object_id in excess of 2^22 ? If so, what happens when you use a GTT. The OBJ column from x$BH for GTT data is reported as the relative data block address of the first block of the segment - and if you have a 'default' build this means a GTT could use the value power(2,22) + 8. So what happens if you have got through 4 million or so table, partition and index definitions, and have a real object at that number ?

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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Original Message ----- From: "Ravi Kulkarni" <kulkarni.ravi_at_heb.com> To: <oracle-l_at_freelists.org> Sent: Tuesday, March 02, 2004 10:51 PM Subject: GTT Locks

> Trying to understand the locking behavior of GTTs (Global Temporary
Tables) :
> (GTT_T is a GTT. T is a regular table)
>
> SQL> insert into gtt_t values (1000);
> 1 row created.
>
> SQL> select object_name, object_type, a.object_id, b.locked_mode from
dba_objects a, v$locked_object b where a.object_id=b.object_id;
> no rows selected
>
> SQL> insert into gtt_t select *from T;
> 1 row created.
>
> SQL> select object_name, object_type, a.object_id, b.locked_mode from
dba_objects a, v$locked_object b where a.object_id=b.object_id;
>
> OBJECT_NAME OBJECT_TYPE OBJECT_ID OBJECT_ID LOCKED_MODE
> ----------------------------------------------------------------
> GTT_T TABLE 204835 204835 3
>
>
> The user acquires a lock on the GTT for performing DML ONLY when selecting
from a Non-GTT.
> 1. How is this different from the first insert on GTT? (In either case, I
noticed a 'TO' lock-type in v$lock)
> 2. Where can I find more info on GTT-peculiarities ?
>
> TIA,
> Ravi.
>
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Received on Wed Mar 03 2004 - 00:48:14 CST