A blocking SQL command prevents other reading or writing operations while it is being executed.

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SSRS Blocking Processes

We have a busy SSRS Reporting server (SQL Server 2008 R2) on which we see frequent blocking between the below processes: [dbo].[CheckSessionLock] [dbo].[WriteLockSession] We are aware that some ...
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Postgresql: Update or insert stuck

I'm running update-or-insert query on a table of approximatelly 3mln rows, 4 columns. Query is part of every day process, and for same days, the query stucks forever. It's just blocked. It's ...
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SQL Server 2012 merge replication blocks other insert/updates during sync

I have a merge replication setup between two SQL Server 2012 databases via Pull method. There are several merge replications affecting different table sets (3 sets 2-5 tables each, actually). There ...
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Trying to add a NULLable column to a table with over 90 million rows takes a very long time

I have been trying to add a NULLable column to a table with over 90 million rows. ALTER TABLE <TableName> ADD <FieldName> INT NULL; It is taking a very long time (been running for over ...
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Why is sql server waiting for acknowledgment?

I have an application that often request a big set of rows [about 20K] from a sql view, in the mean time other applications can't update the table from where the data comes from, the update query's ...
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CLR UDT SCH-M blocking

I’m hoping someone can provide some guidance on a problem I’m having with schema locking on C# CLR UDT’s. I’ve been on the Internet for an extended period of time researching my problem without ...
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Sleeping queries blocking rebuild index and update statistics job in Always on

At one of your client sides we have configured Always on with synchronous mode.Also we have schedule rebuild index and update statistics job which runs in night every alternate day. the issue is ...
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66 views

What happens if two mySQL queries both try to lock the same row at the same time?

So this isn't exactly my strong suit, but here's my basic understanding of the situation: If two threads of the same application both try to execute the same query at the same time, mySQL will ...
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When does SQL Server acquire locks?

The list of isolation levels in SQL Server found here states that write locks acquired within a transaction are retained until the end of the transaction. However it doesn't mention anything about ...
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My connection to a Mysql DB has been blocked after spamming queries, for how long?

I am creating a web application that depends on querying a legacy DB without an API. It's MySql. Off course the lack of an API eventually got me in trouble. A feedback loop while testing the app ...
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Renaming a column with sp_rename hangs SQL Server 2012

I was attempting to remove a column from a table within SQL Server 2012 for one of our developers. As a precaution, before dropping the column, we rename them to make sure that everything continues ...
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How to determine which statement is blocking an update in SQL Server

We have an UPDATE statement running in a large J2EE application that is getting blocked by some other statement. The update is using the primary key, so it should affect only one row. The isolation ...
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Resource cost of a blocked query

I'm currently reviewing a case where an SSRS server is experiencing frequent blocking and deadlocking. The reports are not business-critical, and they are frequently killed to alleviate the blocking. ...
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LCK_M_SCH_M Blocking

I have 2 stored procedures (one vendor, one third party) that are constantly (monthly) stepping on each other. They both (for some reason) acquire a schema lock when all they are doing is updating ...
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50 views

How can I obtain concurrent deletes for this table?

We have a program that is currently doing something to the effect of: SET TRANSACTION ISOLATION LEVEL READ COMMITTED BEGIN TRANSACTION UPDATE [Source].[dbo].[SourceTable] SET [ProcessedOn] = ...
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PostgreSQL: How can I identify the connections which is blocking ALTER TABLE?

I would like to add some fields to a table in all testing and production DBs, all of which are stored in PostgreSQL 9.3 on Amazon RDS. ALTER TABLE users DROP COLUMN IF EXISTS device_language; ALTER ...
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TempDB Query being Blocked

I have been monitoring Blocking issues on our SQL Server database. Very often the below query is running on tempdb and is blocked with LCK_M_S What is this query used for and why does it run ...
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Why is SQL Server's online indexing causing blocking?

My understanding is that online indexing acquires locks at the beginning (Preparation) and end (Final) phases. However, we see a lot of DML queries blocked during the Build phase. A sampling of the ...
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Getting null block_st.text when querying for blocks

We are using the blocking query from this article which queries sys.dm_tran_locks. http://simplesqlserver.com/2013/05/21/blocking-capturing-and-monitoring/ The issue we've ran into is that often ...
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why a session becomes a head blocker

I am troubleshooting a problem that seems to be random The problem is sometimes an application (dynamics SL) is freezing When the application is freezing , I notice there is a blocked by in SQL ...
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570 views

Alter table add column query blocking a table or taking so much time

I'm trying to add a new column to an existing table but it takes so much time or the query is blocking the table, i'm really confused about what's happen exactly. ALTER TABLE MYTABLE1 ADD MYEXPORT9 ...
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How can a blocking_session_id be negative?

I have a case where a query I'm running is taking a long time. When I checked sys.dm_exec_requests the blocking_session_id is a negative value, -2 to be specific. The wait is a LCK_M_X and the ...
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Why am I getting blocked when I call OBJECT_NAME(object_id, database_id) from sys.dm_tran_locks?

I'm working on a query to tell what objects have locks from a given session and I'm running into some blocking issues. Here is my basic query: SELECT request_session_id AS session_id, ...
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Excessive compile blocking on sp_procedure_params_90_rowset

A resurgence of this question Blocked-process-report: what is this waitresource "OBJECT: 32767:124607697:0 [COMPILE] on MSDN: I have caught these statements in Profiler. They all have durations over ...
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Why did my UPDATE statement not complete?

Running SQL Server 2008; Mgmt Studio 2008. I am working with a MS SQL job that we have created for our MS CRM 4.0 implementation. For anyone familiar with CRM, this job purges the aSyncOperationBase ...