Delayed block cleanout and how blocks actually get altered

Hello fellow forumers...
A question about how data|index blocks are actually changed (altered).
Let's suppose that...
A block B1 gets flushed to disk and is removed from the buffer cache before transaction T1, having locked some of its rows, has committed.
Transaction T1 commits while that block is (only) on disk.
Another transaction, T2, pulls the block from disk into the buffer cache, and realizes some of its rows were locked by T1, which, has committed.
Delayed block cleaout occurs (thanks to T2).
But LGWR performed it job, say, long before, while B1 was (only) on disk.
And the redo thread is write only.
So how does B1 gets altered ?
I've read that T2 would do so by using information located in the undo segment that was assigned to T1.
'Seems strange.
Is that right ?
Many, many thanks for your insight.

>
So how does B1 gets altered ?
>
See 'Block Cleanout / Delayed Block Cleanout:' in this article by Oracle ACE director and noted author Jonathan Lewis.
http://jonathanlewis.wordpress.com/2009/06/16/clean-it-up/
>
It’s possible that some of the blocks changed by your transaction were written to disc by dbwr and were even flushed from the buffer cache before you issued the commit. Your session will not re-read these blocks in order to do a commit cleanout on them. In fact, if your transaction was quite large and modified a lot of blocks, it’s quite possible that your session will not even do a commit cleanout on all of the blocks that are still in memory – Oracle doesn’t want to make the user wait for a commit to complete, so it’s a bit lazy about commit cleanout.
At some later point in time another session may read one of those blocks and discover that the ITL includes a transaction that has committed but not been cleaned out. (It can work this out by cross-checking the ITL entry with the relevant transaction table slot in the undo segment header block).
This session will read the commit SCN from the transaction table slot, tidy up the block’s ITL entry, and clear all the related lock bytes. (And it will do this for all committed transactions it finds on the block). This process is known as block cleanout, and because this full cleanout mechanism never takes place on the commit it is more commonly known as delayed block cleanout.
The delayed block cleanout operation changes the block so it generates redo – which is why you may see redo being generated on a select statement, especially after a very big update. (Interestingly, Oracle will report db block changes as this happens – but doesn’t record the block visits as db block gets.)
>
Read the entire article since it covers other scenarios that just the one you ask about and puts everything in the proper context.

Similar Messages

Why are you blocking google and how do i get it back?

I get a blocking message about google. I need google. Why is it being blocked and how do i get it back. What other search sites have you blocked?

Do a malware check with several malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.
Make sure that you update each program to get the latest version of their databases before doing a scan.
*Malwarebytes' Anti-Malware: http://www.malwarebytes.org/mbam.php
*AdwCleaner: http://www.bleepingcomputer.com/download/adwcleaner/ http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
*SuperAntispyware: http://www.superantispyware.com/
*Microsoft Safety Scanner: http://www.microsoft.com/security/scanner/en-us/default.aspx
*Windows Defender: http://windows.microsoft.com/en-us/windows/using-defender
*Spybot Search & Destroy: http://www.safer-networking.org/en/index.html
*Kasperky Free Security Scan: http://www.kaspersky.com/security-scan
You can also do a check for a rootkit infection with TDSSKiller.
*Anti-rootkit utility TDSSKiller: http://support.kaspersky.com/5350?el=88446
See also:
*"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
*https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

Updatetask.exe is repeatedly blocked by my virus checker. Forums say it can be malicious. How do I know, and how do I get rid of it?

I use Firefox on Windows 7. Several times an hour and sometimes when I click a link or do something else when browsing I get a dialog box that says updatetask.exe has been blocked. Forums say this can be a Firefox automatic update executable, but that it can carry malicious baggage.
This file or name does not appear in the Control Panel add/remove programs list, so I can't uninstall it. I don't know if it's safe to just search for and delete the file. So, how do I know if it's authenticaly yours or safe, and how do I get rid of it? The virus checker is F-Secure.

AFAIK. updatetask.exe is a malicious file and it is associated with the Ask.com toolbar. But I'm unsure as it is very tricky, because UpdateTask.exe has 29 different versions, varying from illegal to malignant.
Do a malware check with some malware scanning programs on the Windows computer. 
Please scan with all programs because each program detects different malware. 
All these programs have free versions.
Make sure that you update each program to get the latest version of their databases before doing a scan.
*Malwarebytes' Anti-Malware: http://www.malwarebytes.org/mbam.php
*AdwCleaner: http://www.bleepingcomputer.com/download/adwcleaner/ http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
*SuperAntispyware: http://www.superantispyware.com/
*Microsoft Safety Scanner: http://www.microsoft.com/security/scanner/en-us/default.aspx
*Windows Defender: Home Page: http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
*Spybot Search & Destroy: http://www.safer-networking.org/en/index.html
*Kasperky Free Security Scan: http://www.kaspersky.com/security-scan
You can also do a check for a rootkit infection with TDSSKiller.
*Anti-rootkit utility TDSSKiller: http://support.kaspersky.com/5350?el=88446
See also:
*"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

My iPhone5, 7.0.3, has 725MB of Messages shown in Usage, but no messages in Message App. Where are they and how do I get rid of them??

My iphone5, 7.0.3, has 725MB of Messages shown in Usage, but no messages in Message App. Where are they and how do I get rid of them

Ok, so I think I have found the cause of the problem.
I went to Tools -> Add Ons -> Plug -Ins
Under plug ins I found the zonealarm spy blocker plug in stub
Attached are images of enabled, disabled.
How do I get rid of that space all together, what I mean is, instead of having to choose between a "black space" and a "lego piece space", I want no space.

Bad pop ups and this thing called macsweeper. what us it and how do I get rid of it

I gave bad pop ups and this thing called macsweeper. What is it and how do I get rid of it. Thanks

There is no need to download anything to solve this problem.
You may have installed one or more of the common types of ad-injection malware. Follow the instructions on this Apple Support page to remove it. It's been reported that some variants of the "VSearch" malware block access to the page. If that happens, start in safe mode by holding down the shift key at the startup chime, then try again.
Back up all data before making any changes.
One of the steps in the article is to remove malicious Safari extensions. Do the equivalent in the Chrome and Firefox browsers, if you use either of those. If Safari crashes on launch, skip that step and come back to it after you've done everything else.
If you don't find any of the files or extensions listed, or if removing them doesn't stop the ad injection, ask for further instructions.
Make sure you don't repeat the mistake that led you to install the malware. It may have come from an Internet cesspit such as "Softonic" or "CNET Download." Never visit either of those sites again. You might also have downloaded it from an ad in a page on some other site. The ad would probably have included a large green button labeled "Download" or "Download Now" in white letters. The button is designed to confuse people who intend to download something else on the same page. If you ever download a file that isn't obviously what you expected, delete it immediately.
Malware is also found on websites that traffic in pirated content such as video. If you, or anyone else who uses the computer, visit such sites and follow prompts to install software, you can expect more of the same, and worse, to follow. Never install any software that you downloaded from a bittorrent, or that was downloaded by someone else from an unknown source.
In the Security & Privacy pane of System Preferences, select the General tab. The radio button marked Anywhere should not be selected. If it is, click the lock icon to unlock the settings, then select one of the other buttons. After that, don't ignore a warning that you are about to run or install an application from an unknown developer.
Still in System Preferences, open the App Store or Software Update pane and check the box marked
Install system data files and security updates (OS X 10.10 or later)
or
Download updates automatically (OS X 10.9 or earlier)
if it's not already checked.

Blocked stock and GR Block stock

Can anyone please let me know the difference between Blocked stock and GR blocked stock. How to post stock to these both stock type and how valuation matters to those.
Also for transfer posting from Stock type Blocked Stock to Quality Inspection Stock or Unrestricted-use Stock, whether accounting document will generate or not....
Please clarify me on this.
Thank you
Shreek

Can anyone please let me know the difference between Blocked stock and GR blocked stock. How to post stock to these both stock type and how valuation matters to those.
GR Blocked stocks means if you have doubt about the stock you can post these stocks to GR Blocked stock with mvt type 103.In this case no accounting documents generated.Once you gets clarified the doubt about stock you can move the stock to your stock with mvt 105.Once you post the document with 105 you can get accounting documents will be generated.
Also for transfer posting from Stock type Blocked Stock to Quality Inspection Stock or Unrestricted-use Stock, whether accounting document will generate or not...
Blocked stock is you are blocked these stocks for other movements This stock you can transfer mvt 343 & 344 blocked to unrestricted or unrestricted to block.In this cas you are moving the stocks with in storage location in single plant so thesre is no accounting generated.only stock status changed..
Hope this will clarifies,
JS

What is the little blue bell icon and HOW do I get rid of it?

Hi all,
I keep getting a little blue bell icon with 2 red curved lines up at the top right corner of my screen. I do not have any alarms or alerts set. What is this and how do I get rid of it? (permanently would be nice). Thanks in advance for any wisdom y'all can impart.

Actually neither of the above (I had said I have no alarm set).
Turns out it is the symbol for voicemail calls I didn't receive (thank you from someone else who also has the same problem with their Pearl). To get rid of it one must go into the voicemail area and manually delete those calls.

Hi all. I am new to iPad and am trying to buy certain apps thru iTunes. I keep getting messages saying "this app is not yet available in the South African store"! which means i am unable to buy it. Why not and how can i get around this. Thanks

Hi all. I am new to iPad and am trying to buy / download certain apps thru iTunes and or App Store. I have found the apps i want yet I keep getting messages saying "this app is not yet available in the South African store"! which means i am unable to buy it. Why not and how can i get around this? Thanks

If you see a dialog telling you the app is not avaiable, then it's not available.
And keep in mind, your credit or debit card credentials must be associated with the same country where you reside.
"Although you can browse the iTunes Store in any country without being signed in, you can only purchase content from the iTunes Store for your own country. This is enforced via the billing address associated with your credit card or other payment method that you use with the iTunes Store, rather than your actual geographic location."
From here > The Complete Guide to Using the iTunes Store | iLounge Article

How to actually get help with iWorks or how to return it

I have lost over an hour of work today trying to get some assistance from apple. Bought iworks and the serial number doesn't work. They route me to different people who can't seem to help me. I try to return it and the store doesn't help me. Does anyone know how to get the serial number accepted or how to actually get help from this company or should I consider buying the product a loss and warn colleagues within the university? Thank you!

LeisureG8R:
I also bought iWork online and had it delivered to my office. I didn't want to carry the box home, so I stuck the disk/manual in my bag and threw the box away.
Well, was that a mistake! I realised upon installation that is exactly where the only copy of the serial number is printed.
Or so I thought.
I hit on the idea of going back to the Apple email that notified me of the shipping of my product. On there I found the serial number and simply cut and pasted from there to the dialogue box asking for it during install.
For me that worked. No problems with figures or letters being misread.
Don't know if that's any help.
PowerMac G5 Quad, 2.5GB RAM + PowerBook G4 Ti 15" Mac OS X (10.4.5)

I can't play the downloaded iTunes movie on my newly updated iMac to OS X Maverick. Why not? And How can I get it to work? Thanks.

I can't play the downloaded iTunes movie on my newly updated iMac to OS X Maverick. Why not? And How can I get it to work? Thanks.

Do you get any error message?
What actually happens when you open it?
What app are you trying to play the files inside? Try iTunes.
I assume these files have DRM from the iTunes store. The Mac needs to be authorized to play them, open iTunes & select Authorize in the store menu, then sign in with the Apple ID that purchased the files.
Select the iTem in iTunes & get info on it (from the File menu) & you can see the account name that it belongs to.

I have just sought to update my lightroom and am now unable to access the develop function and get a note stating that I have reduced functionality what it this about and how do I get my product back

I have just sought to update my lightroom and am now unable to access the develop function and get a note stating that I have reduced functionality what it this about and how do I get my product back

Hi there
I have version 5.7 and every time I opened it I was told that updates are available and to click on the icon to access these. Instead it just took me to the
adobe page with nowhere visible to update. I then sought to download lightroom cc and this is when I could not access the 'develop' section due to reduced
functionality It was apparent that my photos had been put in cc but no way to access them unless I wanted to subscribe.
I have since remedied the problem as my original lightroom 5.7 icon is still available on the desktop and have gone back to that. I do feel that this is a bit
of a rip off and an unnecessary waste of my time though.
Thank you for your prompt reply by the way.
Carlo
Message Received: May 04 2015, 04:52 PM
From: "dj_paige" <[email protected]>
To: "Carlo Bragagnolo" <[email protected]>
Cc:
Subject: I have just sought to update my lightroom and am now unable to access the develop function and get a note stating that I have
reduced functionality what it this about and how do I get my product back
dj_paige created the discussion
"I have just sought to update my lightroom and am now unable to access the develop function and get a note stating that I have reduced functionality what it
this about and how do I get my product back"
To view the discussion, visit: https://forums.adobe.com/message/7510559#7510559
>

HT1386 I synced (updated) my iphone to itunes and some songs were deleted from my iphone playlist on my phone. On the computer, a circle is next to the song and the title faded out. What the heck is that all about and how do I get my songs back onto my

I synced (updated) my iphone to itunes and some songs were deleted from my iphone playlist on my phone. On the computer, a circle is next to the song and the title faded out. What the heck is that all about and how do I get my songs back onto my phone playlist? Never happened before. My software is up to date?

http://support.apple.com/kb/HT2519

I put in my memory card to the left side of the computer, but I cannot find the file of pictures anywhere. Its not even on my desktop. What should I do and how can I get it to show up on my desktop?

I put in my memory card to the left side of the computer, but I cannot find the file of pictures anywhere. Its not even on my desktop. What should I do and how can I get it to show up on my desktop?

If your Mac is new-ish and has one of the Lions as its OS, the drives, cards, USB sticks no longer show up, even though they're there. Go to Finder's Preferences and tick the corresponding items in the General and Sidebar tabs.

I just PAID for Black eyed peas Time of my life and now iTunes says I can't put it on my iPod 5th gen ? What? Why? And how can I get it on my ipod?

I just PAID for Black eyed peas Time of my life and now iTunes says I can't put it on my iPod 5th gen ? What? Why? And how can I get it on my ipod? And if I can't put it on my ipod how do I get my money back? I registered my ipod on iTunes, why was a song I can't put on my ipod even offered to me? What a rip?

Because you can only synce with one iTunes library and you are switching libries by using the new computer. To nake this yyour syncing computer:
- Move all the media(apps, music, synced video and photos etc) to the new computer.
- Connect the iPofd yo the computer and bake a backup fo the iPod by right clicking on the iPod under Devices in iTunes and select Back Up
- Restore the iPod from that backup.
Note that the backup that iTunes makes doe not include media.
To move mdia to the new computer see:
iTunes: How to move your music to a new computer
iTunes Store: Transferring purchases from your iOS device or iPod to a computer

HT201317 My photos are syncing from my iPhone, to the iCloud PhotoStream and to our iPad, but it is no longer syncing to my computer (Microsoft, not Apple). Why would this happen and how can I get it resolved?

My photos are syncing from my iPhone to the iCloud PhotoStream and to our iPad, but they are no longer syncing to our home computer (Microsoft operating system, not Apple). Why would this happen and how can I get it resolved? I have since tried to remove and reinstall the iCloud application in my computer's control panel. I have verified that I am using the latest Apple operating system and the latest iTunes. I have reset my photo stream. Not sure what else to try... I was also having an issue with my calendar where it would sync from my computer to my iPhone but not vice versa. Somehow in all the resetting that's resolved, but the photo issue is not. Again - photos are going into the photostream, but not wirelessly being put into the file on my computer.

To change the iCloud ID on your device you have to go to Settings>iCloud, tap Delete Account, provide the password to turn off Find My iPhone when prompted, then sign back in with the ID you wish to use.

Delayed block cleanout and how blocks actually get altered

Similar Messages

Maybe you are looking for