Uwe Hesse

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Windows 7 error “key not valid for use in specified state”

When you see that error upon trying to install or upgrade something on your Windows 7 64-bit machine, chances are that it is caused by a Windows Security update that you need to uninstall. There is probably no point in messing around with the registry or the application that you want to upgrade. Instead, remove the Windows update KB2918614 like this:

Open the control panel, then click  Windows Update

Windows 7 control panelClick Update History and then Installed Updates:

Update HistoryScroll down to Microsoft Windows and look for KB2918614 (I have removed it already before I took the screenshot):

Uninstall KB2918614Finally, hide that update so you don’t get it installed later on again:

Hide KB2918614I’m using a corporate notebook with automatic Windows security updates coming from time to time and encountered that problem while trying to upgrade VirtualBox to version 4.3.12. It is not a VirtualBox issue, though, other installs or upgrades may fail for the same reason. For me, this was a serious problem, because I rely on virtual machines for many demonstrations. Kudos to the virtualbox.org forums! They helped me resolve that problem within a day. Thank you once again, guys! :-)

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Don’t go directly to Maximum Protection!

With a Data Guard Configuration in Maximum Performance protection mode, don’t go to Maximum Protection directly, because that leads to a restart of the primary database:

 Attention!

DGMGRL> show configuration;

Configuration - myconf

  Protection Mode: MaxPerformance
  Databases:
  prima  - Primary database
    physt  - Physical standby database
      physt2 - Physical standby database (receiving current redo)

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> edit configuration set protection mode as maxprotection;
Operation requires shutdown of instance "prima" on database "prima"
Shutting down instance "prima"...
Database closed.
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "prima" on database "prima"
Starting instance "prima"...
ORACLE instance started.
Database mounted.
Database opened.

Instead, go to Maximum Availability first and then to Maximum Protection:

DGMGRL> edit configuration set protection mode as maxperformance;
Succeeded.
DGMGRL> edit configuration set protection mode as maxavailability;
Succeeded.
DGMGRL> edit configuration set protection mode as maxprotection;
Succeeded.

The demo was done with 12c, involving a cascading standby database, but the behavior is the same in 11g already. The odd thing about it is that DGMGRL will restart the primary without warning. Wanted to share that with the Oracle community for years but always got over it somehow.

,

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Why Write-Through is still the default Flash Cache Mode on #Exadata X-4

The Flash Cache Mode still defaults to Write-Through on Exadata X-4 because most customers are better suited that way – not because Write-Back is buggy or unreliable. Chances are that Write-Back is not required, so we just save Flash capacity that way. So when you see this

CellCLI> list cell attributes flashcachemode
         WriteThrough

it is likely to your best :-)
Let me explain: Write-Through means that writing I/O coming from the database layer will first go to the spinning drives where it is mirrored according to the redundancy of the diskgroup where the file is placed that is written to. Afterwards, the cells may populate the Flash Cache if they think it will benefit subsequent reads, but there is no mirroring required. In case of hardware failure, the mirroring is already sufficiently done on the spinning drives, as the pictures shows:

Flash Cache Mode Write-Through

Flash Cache Mode WRITE-THROUGH

That changes with the Flash Cache Mode being Write-Back: Now writes go primarily to the Flashcards and popular objects may even never get aged out onto the spinning drives. At least that age out may happen significantly later, so the writes on flash must be mirrored now. The redundancy of the diskgroup where the object in question was placed on determines again the number of mirrored writes. The two pictures assume normal redundancy. In other words: Write-Back reduces the usable capacity of the Flashcache at least by half.

Flash Cache Mode Write-Back

Flash Cache Mode WRITE-BACK

Only databases with performance issues on behalf of writing I/O will benefit from Write-Back, the most likely symptom of which would be high numbers of the Free Buffer Waits wait-event. And Flash Logging is done with both Write-Through and Write-Back. So there is a good reason behind turning on the Write-Back Flash Cache Mode only on demand. I have explained this just very similar during my present Oracle University Exadata class in Frankfurt, by the way :-)

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