SQL Server misunderstanding 30th about the 17th day about page checksum error _mssql

In fact, I've already had articles detailing page checksums: How do I tell if the IO subsystem is causing corruptions?

Misunderstanding #17: Several misunderstandings about page checksum

The basics of the spread are wrong.

Pages checksum (page CheckSum) automatically opens after upgrading from SQL Server 2000 or 7.0

In fact, the database upgraded from the old instance does not automatically open the page checksum unless you explicitly use ALTER DATABASE databasename SET page_verify checksum to open it. The new database page checksum in SQL Server 2005 or 2008 is opened by default.

Page checksum can correct errors

Page checksums can only find errors, not the same as the CRC code in Network protocols, which corrects an error.

when the page checksum is turned on, the page checksum is started for each page in the database .

Error, in fact, when the page checksum is turned on, no thread will modify the page in the foreground or in the background. Page checksums are added to the page only when you rebuild the index or modify the page.

d) Reading the page can be officers transferred Guevara and added to the page

Error, the page can be validated and added to the page only after it has been read to memory and modified, and then written back to the disk.

e) All Torn-page detection information will be lost when the page validation mode of the database is changed from torn-page detection to page checksum

Error, every page knows that its protection mode is Torn-page detection, page checksum or none at all. As previously stated, only the page validation will be modified after the pages have been modified (that is, a database can exist some pages are torn-page detection, others are page checksums). I have an article detailing this section in more detail: Inside the Storage engine:does turning on page checksums discard any torn-page protection?

Page checksum can be detected as soon as an error occurs

This myth was revealed by SQL Server MVP Gail Shaw. Of course, it's also wrong, and the damaged page will not be discovered until it is read into the memory buffer pool for validation.