The isolation-level tag has no wiki summary.
1
vote
2answers
44 views
Read Committed Isolation Level
Quote from docs:
Read Committed is the default isolation level in PostgreSQL. When a transaction uses this isolation level, a SELECT query (without a FOR UPDATE/SHARE clause) sees only data ...
5
votes
2answers
124 views
ALLOW_SNAPSHOT_ISOLATION and READ_COMMITTED_SNAPSHOT
Most of the forum and example online always suggest to have both ALLOW_SNAPSHOT_ISOLATION and READ_COMMITTED_SNAPSHOT set to ON whenever someone is asking snapshot, row versioning or similar question. ...
1
vote
0answers
32 views
Does SQL Server place shared locks on scanned records when using REPEATABLE READ [duplicate]
Assume a SQLCmd session which is using transaction isolation level REPEATABLE READ.
In this session I start a transaction and execute an UPDATE statement with a WHERE clause on a non indexed column. ...
3
votes
2answers
74 views
Does SQL Server place shared locks on scanned records when using REPEATABLE READ
Assume a SQLCmd session which is using transaction isolation level REPEATABLE READ.
In this session I start a transaction and execute an UPDATE statement with a WHERE clause on a non indexed column. ...
1
vote
1answer
193 views
Execution of sequential delete and uncommitted read
We are running the following queries using dynamic SQL, which is erroring out for few cases when we run concurrent instances. The error is:
Could not continue scan with NOLOCK due to data ...
0
votes
0answers
40 views
What would this non-'unique index with a unique search condition` query lock?
I am not sure about this part of the transaction manual
For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), UPDATE, and DELETE statements, locking depends on whether the statement ...
0
votes
1answer
147 views
Does TRUNCATE TABLE affects isolation level in Sql Server?
As I am working on the project which has SQL SERVER as a database....I'm maintaining isolation level in my project where I enabled snapshot isolation level for my project....
As I have to make some ...
5
votes
2answers
147 views
SQL Server Select Count READ_COMMITTED_SNAPSHOT QUESTION
I seem to be getting a lot of deadlocks when doing select count(*) on a particular table.
I have already changed all the required parameters and made them into row only locking.
I've also changed the ...
5
votes
4answers
486 views
MySQL InnoDB locks primary key on delete even in READ COMMITTED
Preface
Our application runs several threads that execute DELETE queries in parallel. The queries affect isolated data, i.e. there should be no possibility that concurrent DELETE occurs on the same ...
5
votes
1answer
95 views
Determining which isolation level is appropriate
This is a homework question.
For the following transactions state the isolation level that will
maximize throughput without lowering the integrity of the database.
Explain the answer.
...
3
votes
1answer
267 views
How to force the use of row locks?
I am trying to get my table to use row locks. I have already disabled lock escalation. The isolation level is READ_COMMITTED_SNAPSHOT
alter table <TABLE_NAME> SET (LOCK_ESCALATION=DISABLE)
go
...
4
votes
2answers
148 views
Isolation Level for a Data Warehouse
We are building out a data warehouse (and also some data marts as well) in our organization. My DBA skills have mostly been on OLTP type applications, but I am moving into supporting OLAP for our ...
4
votes
2answers
153 views
Schema blocking in READ_COMMITTED_SNAPSHOT
I am trying to troubleshoot locking behavior and the READ_COMMITTED_SNAPSHOT isolation level while attempting to resolve concurrency issues.
Background: Assume an online ordering system (ecommerce). ...
8
votes
1answer
251 views
Are SQL Server Database writes slower with Snapshot Isolation?
I have a lot of deadlocks going on in my system.
I would like to use Snapshot Isolation to fix them, but my DBA has reserves about it.
One of his concerns is that Snapshot Isolation slows down ...
3
votes
3answers
206 views
Does Snapshot Isolation only give you what has been commited? (And General Snapshot Isolation questions.)
So, I have some deadlocking issues.
I have seen two options to resolve it. Add read uncommitted to my db or do Snapshot Isolation and add read committed snapshot.
After doing some research into ...
5
votes
1answer
146 views
Does the transaction isolation level affect indices as well?
Here's one for the SQL Server gurus: if I set my SQL Server 2008 transaction isolation level to READ UNCOMMITTED, does that also affect the index pages?
E.g. using ISOLATION LEVEL READ UNCOMMITTED, ...
2
votes
2answers
472 views
What effect does serializable isolation level have on DDL-statements?
I'm using Red Gate SQL Compare to create a release script based on differences between SVN and a database. This results in a script containing a bunch of table- and procedure-changes and it works ...
13
votes
3answers
1k views
Managing concurrency when using SELECT-UPDATE pattern
Let's say you have the following code (please ignore that it's awful):
BEGIN TRAN;
DECLARE @id int
SELECT @id = id + 1 FROM TableA;
UPDATE TableA SET id = @id; --TableA must have only one row, ...
5
votes
3answers
1k views
SQL Server - what isolation level for non-blocking select statements?
I have a long running transaction (called, say, T1) that performs some deletes, updates and inserts on a table in SQL Server 2008 R2. At the same time, another process periodically runs select ...
