odd deadlocking behaviour

I am running SQL Server 2000 SP3a on a single processor computer and:
I have a table with the following columns
CREATE TABLE [dbo].[SP148_JOB_AHO_PERIODS] (
[JOB_NO] [int] NOT NULL ,
[OVERRIDDEN_PERIOD_START] [datetime] NULL ,
[OVERRIDDEN_PERIOD_END] [datetime] NULL
) ON [PRIMARY]
GO
That has the following data:
1,06/01/2003 17:00:00,NULL
2,NULL,13/01/2003 08:00:00
2,13/01/2003 17:00:00,NULL
3,NULL,20/01/2003 08:00:00
3,20/01/2003 17:00:00,NULL
4,NULL, 27/01/2003 08:00:00
4,27/01/2003 17:00:00,NULL
If I now try deleting these rows from two database sessions in the order as
seen below I end up with a deadlock:
Firstly on SPID 56:
set implicit_transactions on
delete from SP148_JOB_AHO_PERIODS where job_no = 2
Secondly on SPID 57:
set implicit_transactions on
delete from SP148_JOB_AHO_PERIODS where job_no = 1
... This then blocks ? Which I am not sure about.
Thirdly back on SPID 56:
delete from SP148_JOB_AHO_PERIODS where job_no = 6
Creates a deadlock victimising SPID 57.
I accept that this table does not have a primary key but when I add one it
still deadlocks.
Why, on step 2, does SPID 57 lock when I delete the row where job_no = 1?
Why does a deadlock occur when SPID 56 subsequently deletes the row where
job_no is 6 i.e. no rows?
When I looked at sp_lock output it appeared that both sessions were waiting
on the same RID, does this mean that a RID is not necessarily 1 database
table row?
Thanks- What kind of lock triggered the deadlock? row, index, page, extent, table,
database
- Do you have an index by "job_no"?
AMB
"Tony Jones" wrote:

> I am running SQL Server 2000 SP3a on a single processor computer and:
> I have a table with the following columns
> CREATE TABLE [dbo].[SP148_JOB_AHO_PERIODS] (
> [JOB_NO] [int] NOT NULL ,
> [OVERRIDDEN_PERIOD_START] [datetime] NULL ,
> [OVERRIDDEN_PERIOD_END] [datetime] NULL
> ) ON [PRIMARY]
> GO
> That has the following data:
> 1,06/01/2003 17:00:00,NULL
> 2,NULL,13/01/2003 08:00:00
> 2,13/01/2003 17:00:00,NULL
> 3,NULL,20/01/2003 08:00:00
> 3,20/01/2003 17:00:00,NULL
> 4,NULL, 27/01/2003 08:00:00
> 4,27/01/2003 17:00:00,NULL
> If I now try deleting these rows from two database sessions in the order a
s
> seen below I end up with a deadlock:
> Firstly on SPID 56:
> set implicit_transactions on
> delete from SP148_JOB_AHO_PERIODS where job_no = 2
> Secondly on SPID 57:
> set implicit_transactions on
> delete from SP148_JOB_AHO_PERIODS where job_no = 1
> ... This then blocks ? Which I am not sure about.
> Thirdly back on SPID 56:
> delete from SP148_JOB_AHO_PERIODS where job_no = 6
> Creates a deadlock victimising SPID 57.
> I accept that this table does not have a primary key but when I add one it
> still deadlocks.
> Why, on step 2, does SPID 57 lock when I delete the row where job_no = 1?
> Why does a deadlock occur when SPID 56 subsequently deletes the row where
> job_no is 6 i.e. no rows?
> When I looked at sp_lock output it appeared that both sessions were waitin
g
> on the same RID, does this mean that a RID is not necessarily 1 database
> table row?
> Thanks|||Turn on trace flag 1204 and -1. Then your answers will be in the errorlog.
"Alejandro Mesa" <AlejandroMesa@.discussions.microsoft.com> wrote in message
news:5E921D65-22E3-40D0-AE4C-BEBF76DF8FC7@.microsoft.com...[vbcol=seagreen]
>- What kind of lock triggered the deadlock? row, index, page, extent,
>table,
> database
> - Do you have an index by "job_no"?
> AMB
> "Tony Jones" wrote:
>|||The blocked SPID 57 is waiting on a RID (so a row lock) both SPIDs are
waiting on the same rid i.e. the same fileid:pageid:slot, hence the question
is the RID locking more than one row?
No I have not had a index on job_no I have tried a primary kry on a new
column defined to be the Identity column. This produced the same deadlock
behaviour.
"Alejandro Mesa" wrote:
[vbcol=seagreen]
> - What kind of lock triggered the deadlock? row, index, page, extent, tabl
e,
> database
> - Do you have an index by "job_no"?
> AMB
> "Tony Jones" wrote:
>