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Showing posts with label Deadlock. Show all posts
Showing posts with label Deadlock. Show all posts

Wednesday, September 10, 2014

Stimulating DEADLOCK in SQL Server

Here in this article we are trying to stimulate Deadlock situation, we are trying to create two table table1 and table2 for the same purpose

create table table1
(id int identity(1,1),
col2 int)

create table table2
(id int identity(1,1),
col2 int)

Command(s) completed successfully.

Now lets insert few records in both the table.

insert into table1
select 10 union all
select 20 union all
select 30

insert into table2
select 100 union all
select 200 union all
select 300

No w open a session by opening a new query window in SSMS, I will call it session1 and try to execute the below code, here we opened a transaction then updating table1 col2 where id =1

begin tran
       update table1
       set col2 = col2 + 10
       where id = 2

Now open another query window (second session) in SSMS and execute the below statement, here we are trying to update both the table the second table will wait for first transaction to unlock table1 for its update. And it goes on execution for infinite time.

begin tran
       update table2
       set col2 = col2 + 100
       where id = 2

       update table1
       set col2=col2 + 10
       where id = 2
commit tran

Now again come back to session1 window and execute the below code

update table2
set col2 = col2 + 100
where id = 2

now as you run this above statement on session1, SQL Server sense deadlock since the above code wait for table2 to get unlocked by session2 and same way session2 waits for session1 for table1 to unlock and DEADLOCK occurs, in this case SQL server chosen session1 as victim and abort session1 with a message

Msg 1205, Level 13, State 45, Line 7
Transaction (Process ID 55) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

And session 2 will complete automatically.

There are no nights for SQL Developers, if so please give me address  J


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