Click here to monitor SSC
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Ghost Records


Ghost Records

Author
Message
Steve Jones
Steve Jones
SSC Guru
SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)SSC Guru (50K reputation)

Group: Administrators
Points: 50733 Visits: 19003
Comments posted to this topic are about the item Ghost Records

Follow me on Twitter: @way0utwest
Forum Etiquette: How to post data/code on a forum to get the best help
My Blog: www.voiceofthedba.com
Peter Trast
Peter Trast
Say Hey Kid
Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)Say Hey Kid (664 reputation)

Group: General Forum Members
Points: 664 Visits: 655
First to answer and got it right! Never heard of it but the right answer was perfectly logical.

Great question!

Peter Trast
Microsoft Certified ...(insert many literal strings here)
Microsoft Design Architect with Alexander Open Systems
M&M
M&M
Hall of Fame
Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)Hall of Fame (3.3K reputation)

Group: General Forum Members
Points: 3257 Visits: 3904
I remember reading about this in an article.

M&M
khullargirish02
khullargirish02
Old Hand
Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)Old Hand (395 reputation)

Group: General Forum Members
Points: 395 Visits: 126
When rows are marked as deleted after a DML operation and the transaction is committed, the rows become Ghost records.

I got it right Smile
Kwex
Kwex
Old Hand
Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)Old Hand (349 reputation)

Group: General Forum Members
Points: 349 Visits: 240
Nice to know! DB2 behaves quite differently, because it just re-uses the page after records have been marked as deleted. It doesn't need an extra background process (ghost exorciser) to make a physical delete.

Not sure why SQL Server adopted this approach :-)

Kwex.
dave.clark
dave.clark
Valued Member
Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)Valued Member (69 reputation)

Group: General Forum Members
Points: 69 Visits: 555
I believe it is done for performance reasons. Deleting data can occur faster and rollbacks would be faster. Then a process can later update clear up the ghost records.
chrisfradenburg
chrisfradenburg
SSCommitted
SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)

Group: General Forum Members
Points: 1900 Visits: 2061
As to why something goes through and cleans up the ghost records instead of just allowing the space get reused, that way the data doesn't remain on disk so it doesn't accidentally read by something. Or purposefully read by someone for that matter.
GilaMonster
GilaMonster
SSC Guru
SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)SSC Guru (73K reputation)

Group: General Forum Members
Points: 73259 Visits: 44965
cfradenburg (6/2/2011)
As to why something goes through and cleans up the ghost records instead of just allowing the space get reused, that way the data doesn't remain on disk so it doesn't accidentally read by something. Or purposefully read by someone for that matter.


Ghost cleanup doesn't overwrite the ghosted rows. A direct read of the data file can see deleted data well after the ghosted rows are removed.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
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


chrisfradenburg
chrisfradenburg
SSCommitted
SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)SSCommitted (1.9K reputation)

Group: General Forum Members
Points: 1900 Visits: 2061
Interesting. What does the ghost cleanup process do then?
SQLRNNR
SQLRNNR
One Orange Chip
One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)One Orange Chip (27K reputation)

Group: General Forum Members
Points: 27132 Visits: 18342
GilaMonster (6/2/2011)
cfradenburg (6/2/2011)
As to why something goes through and cleans up the ghost records instead of just allowing the space get reused, that way the data doesn't remain on disk so it doesn't accidentally read by something. Or purposefully read by someone for that matter.


Ghost cleanup doesn't overwrite the ghosted rows. A direct read of the data file can see deleted data well after the ghosted rows are removed.


Sounds like a fun experiment...



Jason AKA CirqueDeSQLeil
I have given a name to my pain...
MCM SQL Server, MVP


SQL RNNR

Posting Performance Based Questions - Gail Shaw

Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search