Re: q: diffrence between row_shared and row_exclusive lock ?

sybrand, here is my test.

richard,

#1

ADDR KADDR SID TY ID1 ID2 LMODE REQUEST -------- -------- ---------- -- ---------- ---------- ---------- ----------

     CTIME BLOCK
---------- ----------

6BBA6284 6BBA6390          9 TX     458773       1083          6          0
       187          0

6BB4E074 6BB4E088          9 TM      30139          0          2          0
       187          0

6BB4E0F8 6BB4E10C         10 TM      30139          0          3          0


In #1 sid 9 (select .. for update). tm lock lmode=2
      another session (sid=10) I can lock the same table with row exclusive
      (lmode =3). in both cases id1 = 30139
         

#2

ADDR KADDR SID TY ID1 ID2 LMODE REQUEST -------- -------- ---------- -- ---------- ---------- ---------- ----------

     CTIME BLOCK
---------- ----------

6BB4E074 6BB4E088          9 TM      30139          0          3          0
        65          0

6BB4E0F8 6BB4E10C         10 TM      30139          0          3          0
        30          0

In #2 sid=9 lock table(30139) in row exclusive mode (lmode=3)
      sid=10 can lock the same table(30139) with row exclusive mode(lmode=3)

What you say is true in most literature and I am confused because my testing can not prove it. I'm confused.

thnx ted

Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote in message news:<tm6ijugh8nc66adje9qeehb2kn1e847283_at_4ax.com>...
> On 19 Jul 2002 23:17:36 -0700, tedchyn_at_yahoo.com (Ted Chyn) wrote:
>
> >all,
> >
> >row shared lock lmode=2
> >row exclusive lock lmode=3
> >
> >row shared is more restrictive than row exclusive.
> >row shared can be generated with select ... for update of
> >row exclusive can be generated with lock table in row exclusive mode
> >or update statement.
> >
> >
> >
> >Can any one give me an working example explaining what are difference
> >between these two type locks - in terms why one is more restritive
> >than the other?
> >
> >thnx in advance
> >ted chyn
>
> row share: others can read
> rows exclusive: access is completely blocked
>
> Hth
>
>
> Sybrand Bakker, Senior Oracle DBA
>
> To reply remove -verwijderdit from my e-mail address
Received on Sat Jul 20 2002 - 23:37:41 CDT