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Hi Howard
I have some doubts about row shared locks as well, from your post
Do you mean the meaning of *share* is sharing the table lock....???? Or it is really that the locked row can be shared.... well I am not very clear because I dont really understand what's the meaning of share here. I have always thought that a row is always locked exclusively. i.e if one is trying to updating a row no matter with pure update or select... for update the row is locked and noone else can lock that row
Howard J. Rogers wrote:
> "Ted Chyn" <tedchyn_at_yahoo.com> wrote in message
> news:44a19320.0207202037.430ff971_at_posting.google.com...
>
>>sybrand, here is my test. >> >>richard, >> >> >>#1 >> >>ADDR KADDR SID TY ID1 ID2 LMODE >>
>>-------- -------- ---------- -- ---------- ---------- ---------- --------- >>
>> CTIME BLOCK >>---------- ---------- >>6BBA6284 6BBA6390 9 TX 458773 1083 6 >>
>> 187 0 >> >>6BB4E074 6BB4E088 9 TM 30139 0 2 >>
>> 187 0 >> >>6BB4E0F8 6BB4E10C 10 TM 30139 0 3 >>
>> >>In #1 sid 9 (select .. for update). tm lock lmode=2 >> another session (sid=10) I can lock the same table with row >>
>> (lmode =3). in both cases id1 = 30139 >> >>
>>#2 >> >>ADDR KADDR SID TY ID1 ID2 LMODE >>
>>-------- -------- ---------- -- ---------- ---------- ---------- --------- >>
>> CTIME BLOCK >>---------- ---------- >>6BB4E074 6BB4E088 9 TM 30139 0 3 >>
>> 65 0 >> >>6BB4E0F8 6BB4E10C 10 TM 30139 0 3 >>
>> 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 >>
>>What you say is true in most literature and I am confused because my >>
>>can not prove it. I'm confused. >> >> >>thnx ted >> >> >> >>Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote in message >>
>>>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 >>>