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  • Blog Post: Concurrency Series: My application was running fine yesterday but why is it blocking today?

    Please refer to for details. Cross-referencing here Thanks Sunil Agarwal
  • Blog Post: Concurrency Series: Minimizing blocking between updaters

    Please refer to for details. Cross referencing my post. Thanks Sunil Agarwal
  • Blog Post: Concurrency Series: Why do I get blocked when no one has locked the row(s) being queried?

    Please refer to for details Thanks Sunil Agarwal
  • Blog Post: Concurrency Series: Why do I get blocking when I use Read Uncommitted isolation level or use NOLOCK hint?

    I posted this in SQLCAT blog site. This post provides reference to Thanks Sunil Agarwal
  • Blog Post: Concurrency Series: Basics of Transaction Isolation Levels

    Please refer to the blog Thanks Sunil Agarwal
  • Blog Post: Concurrency Series: Common Concurrency Issues with Applications

    As part of my role as a program manager in SQL Server Engine, one of the areas I am reponsible for is the concurrency related features in SQL Server. If you have been involved with database applications as a develeoper or as a DBA in keeping the application running, I am sure you will agree that blocking...
  • Blog Post: Improvement in minimizing lockhash key collisions in SQL Server 2008R2 and its impact on concurrency

    Another improved functionality in SQL Server 2008 R2 I am posting this on behalf of Juergen Thomas who has been with SQL Server PM team from 12+ years and is an expert in SAP. Juergen>> In this article I’d like to talk about another improvement we made to SQL Server 2008 R2. The improvement...
  • Blog Post: Overhead of Row Versioning

    Last week I was teaching a class on snapshot isolation and we discussed the overheads of snapshot isolation. There are three main overheads that you need to be aware of when you enable snapshot isolation read-committed-snapshot on a database. First, each UPDATE/DELETE operation generates a row version...
  • Blog Post: Read-Only filegroups and Locking

    I recently saw a newsgroup post that sort of implied that accessing data residing on read-only filegroups can save you on locking. Well, it could, but it does not. If you really want to save on locks, the whole database needs to be set to read-only. Back to read-only filegroups. They provide you...
  • Blog Post: Troubleshooting deadlocks in SQL2005

    Deadlock in the context of SQL Server means two or more transactions or tasks are waiting on each other to acquire the resources needed to complete. A resource can be a logical lock or can be memory grant or can be a worker thread and so on. Normally, when a transaction T1 requests a lock to access...
  • Blog Post: Range locks

    Lately I have seen some quesitons on range locks. Why certain keys are locked? How is this behavior different for unique vs. non-unique indexes? So I played around with range locks and here are my findings so far. Range locks are obtained on index keys to prevent phantoms when you execute transactions...
  • Blog Post: Lock Escalation in SQL2005

    Lock Escalation: If you consider the hierarchy of the objects in a SQL Server instance, at the top level you have the database, followed by schema, tables, table partitions, pages and then finally the individual rows. If you acquire a lock at higher level, it can cover more resources there by you...
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