0
votes
0answers
39 views

Why does the delete/update block each other in this case?

The following drives me crazy. I have: session1>begin; session2>begin; session2>update dummy set salary=1000 where id=11; session1>delete from dummy where id=1; id is the PK ...
1
vote
1answer
68 views

How does the transactions interact if you set a different isolation level per connection?

I read that I can have different isolation levels per connection and in the server. The default isolation level is REPEATABLE-READ. So if I have a transaction that issues a SERIALIZED to the client ...
1
vote
2answers
69 views

Transaction basics. What is the result of 2 transactions running concurrently?

I have a rather basic question on transactions. Assume a table Account with a column amount. Now we have the following code: BEGIN $amount = SELECT amount FROM ACCOUNT WHERE id = 123; $amount = ...
1
vote
1answer
164 views

DB Locks - How would one handle long transactions and maintain high concurrency?

We're maintaining a POS/WMS Application built in powerbuilder that runs on SQL Server 2008 R2 backend. Recently, we've been having a lot of locking issues and I believe it has to do with how we handle ...
0
votes
1answer
104 views

What causes lost updates being observed in my SQL Azure database?

I have a SQL Azure database with the following tables: CREATE TABLE [dbo].[UserBalances] ( [UserId] UNIQUEIDENTIFIER UNIQUE NOT NULL DEFAULT NEWID(), [AvailableMoney] INT NOT NULL ...
1
vote
1answer
66 views

How, when and why does implicit changing of transaction isolation level happen?

RCSI (Read Committed Snapshot Isolation) is the setting of a database changing the behavior of (the default) Read Committed isolation level in SQL Server. This is, as I understand, the context of ...
0
votes
1answer
708 views

Putting a Select statement in a transaction

What is the difference between these 2 queries: start transaction; select * From orders Where id=1; UPDATE orders SET username="John" Where id=1; commit; And without transaction: select * From ...
2
votes
1answer
623 views

unique constraint violated (ORA-00001) in concurrent insert [closed]

I have a procedure that is called from concurrent transactions: //Some actions here INSERT INTO table1 (table1_id, table1_val1, table1_val2, table1_val3) VALUES ...
1
vote
1answer
159 views

timestamp based concurrency

I am wondering if someone could help me out with a question I have about time stamp based concurrency. I found the following practice problem on a website It basically asks which of the following ...
4
votes
2answers
2k views

Concurrent Transactions vs Simultaneous Transactions

Chapter 6 of David Kroenke's Database Concepts: Database Administration Is my understanding correct that in a database, simultaneous transactions don't really happen. Instead, it is a concurrent ...