Question: Does NOLOCK Really Applies No Lock?
Answer: The answer is NOLOCK do apply the lock and it is Sch-S lock. Sch-S stands for Schema Stability. Quite a few people say it is actually Schema Shared lock and it is not correct.
SQL SERVER – Applying NOLOCK to Every Single Table in Select Statement – SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
The other day, during SQL Server Performance Tuning Practical Workshop, I walked into a very interesting situation. While tuning a query we had a situation when we had to check if the query is locked during the execution of not. To test our theory out we had to put a nolock hint for every single table of the long query. However, it was no way possible to do so as the Stored Procedure was super huge and involved over 90 tables and 14 views in multiple SQL Statements. It was indeed a huge challenge for a developer team to modify that SP. If you ever face such situations, you should not stress out. There is a much simpler way to read uncommitted data.
SQL SERVER – Observation: ROWLOCK Hint and Slow Performance
During my recent Comprehensive Database Performance Health Check Developer showed me a slow query which used ROWLOCK hint. The common understanding is that with the help of ROWLOCK hint SQL Server only locks a single row which eventually leads to performance but in their case, it was actually very much opposite. Let us see this scenario with a simple example.
SQL SERVER – Difference Between NOLOCK and NOWAIT Hints
It is interesting to see how a blog evolves with the time and user interacts with each blog post. Earlier I wrote two of the blog posts on NOWAIT and SET LOCK_TIMEOUT. I have received very good response on this subject. Please read following two blog posts before continuing this blog post.
SQL SERVER – Basic Explanation of SET LOCK_TIMEOUT – How to Not Wait on Locked Query
In earlier blog post SQL SERVER – Basic Explanation of Query Hint NOWAIT – How to Not Wait on Locked Query, we learned how we can use NOWAIT query hint to not wait on any locked query and return error. The Query Hint works on query and table level. There is…
Read MoreSQL SERVER – Basic Explanation of Query Hint NOWAIT – How to Not Wait on Locked Query
Everybody knows about NOLOCK Â but not everyone knows about NOWAIT. They are different and they have an entire different purpose. In this blog post we will not talk about NOLOCK but we will see how NOWAIT will work. The idea of writing about blog post is based on the question…
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Puzzle – Usage of New Index Hints – ForceSeek and ForceScan
Tomorrow is the weekend. I just thought, let us explore something new but a quick puzzle to explore about index hints.
SQL Server Denali has new Query Hint – FORCESCAN. In earlier version of SQL Server we already have Query Hint FORCESEEK but now the counter part also exists. The quick understanding is there will be cases when FORCESEEK or FORCESCAN will be helpful and improve the performance of the query.