Internals of data insertion into the table

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Internals of data insertion into the table

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SQL*

Posted Tuesday, September 25, 2012 12:50 AM

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Hi,

When we insert the data into a table, what happened exactly(process)?

How the data will be inserted? For any modifications sql server uses t-log right? How the t-log will be committed to data pages?

Thanks,

Smile

Post #1363816

sroos

Posted Tuesday, September 25, 2012 1:51 AM

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The transaction log is used for all modifications to guarantee atomicity, durability and consistency. Read Gail's thorough article.

http://www.sqlservercentral.com/articles/Administration/64582/

Post #1363841

GilaMonster

Posted Tuesday, September 25, 2012 2:52 AM

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The transaction log records aren't committed to data pages. The data modification is made to the data pages (in memory) and then logged into the transaction log. The only time you get replay from the log is in database recovery or restores (or on the mirror DB in database mirroring).

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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Post #1363861

SQL*

Posted Tuesday, September 25, 2012 3:24 AM

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GilaMonster (9/25/2012)

The data modification is made to the data pages (in memory) and then logged into the transaction log.

That means
1. Sql server fetches the table related data pages to memory (What is the memory in this case is it RAM?)
Q. How many pages will be fetched to Memory?
Q2. How does server knows that the pages are related to a table?

if i am wrong can u correct me, Can you tell me the process of insertion?

Thanks alot

Smile

Post #1363876

Grant Fritchey

Posted Tuesday, September 25, 2012 4:25 AM

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There are scads and scads of processes that take place when you insert data. I'd suggest getting a copy of Kalen Delaney's book SQL Server Internals. That covers the process in wonderful detail much better than you're going to get in a simple forum post.

May I ask, what specifically are you trying to understand about it? Are you hitting some type of problem?

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Post #1363918

GilaMonster

Posted Tuesday, September 25, 2012 4:36 AM

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SQL* (9/25/2012)

Q. How many pages will be fetched to Memory?

As many as are needed for the query

Q2. How does server knows that the pages are related to a table?

In short, the allocation pages (or which there are many kinds) and the system tables.

Read Kalen's book, read Paul Randal's blog.

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Post #1363925

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