IE Cache

[Diancecht]

Hi all. I've posted this in the Browsers forum, but as it's highly related to XP, maybe someone here has thoughts to share.

I'm playing around with offline content and cache in IE. My goal is to have some offline content avaliable for the user so he never needs to download it from the net.

But I'm facing some issues that are surprising me, and I wondered if anyone has thoughts about it:

1.- When I set a limit to the size of the temporary internet files on disk, I can see that the downloaded files size is bigger than that limit.

2.- From time to time, the limit is respected, and the offline content is deleted. I must admit I didn't expect this behaviour. I expected offline content not to interfere with cache size.

I was looking for articles that explain the exact behaviour of this cache, but no joy so far.

I'd thank any comment or link you could provide.

Cheers,
Dian

 

[cdogg]

[blue]I expected offline content not to interfere with cache size[/blue]"

Let's define "offline content". Are you talking about favorites that are made "available offline" so that you can view them without a connection, or are you just talking about random images/text/links that are stored on the hard drive when you visit a page? When you refer to cache, I'm assuming you mean anything in the "Temporary Internet Files" folder.

The source of your confusion might be that offline content is cache, unless you make a webpage available offline which is separate. Also keep in mind that in addition to the cache size, there is a cache time limit setting. So when the time expires, content is deleted at will. In addition, webpage updates or changes on the server can cause content to get swapped out on the fly locally on the hard drive.

As for the size problem you encountered, I'm not sure. What folder(s) were you monitoring?

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[Diancecht]

Hi cdogg

Sorry for being so vague, I'll try to be more concrete.

What I mean with "offline content" is exactly those favorites that you make avaliable offline. And the folder I'm monitorizing is the "Temporary Internet Files" folder.

What I'm trying to achieve is to make some content avaliablo offline for a set of users. As this content is treated like a cache, they wouldn't need to download this content from the net everytime the browser is started (the empty Temporary Folder on exit needs to be activated)

This works so far, the content is downloaded and the user surfs happily without bandwith consum.

My next concern was: what happens if the cache size limit is reached? I'd expect IE to delete oldest files, but just cached ones, not those downloaded to browse offline.

Sometime I can find cached items size is bigger than cache limit, I guess there's a process that checks that and delete then from time to time.

I hope this clarifys the things a little.

Cheers,
Dian

 

[cdogg]

[blue]I hope this clarifys the things a little[/blue]"

Yes it did, thanks.

Here's the deal. It's my understanding that using the "Make available offline" option stores files elsewhere on the hard drive. The data is not stored under the "Temporary Internet Files" folder. It is also my understanding that this offline content is not used by Internet Explorer unless the connection is lost.

Therefore, deleting the cache from "Tools -> Internet Options" shouldn't affect it, nor should your settings regarding date and size.

These links might help:

http://www.pcguide.com/vb/showpost.php?p=112357&postcount=5

http://technet2.microsoft.com/Windo...0c4c-40bf-8a83-bb436b1810c71033.mspx?mfr=true

http://www.milincorporated.com/a-temporary-internet-files.html

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[Diancecht]

Thanks for the links, they're really clarifying.

From one of them:

Temporary Internet Files improve speed of web browsing and also make possible so called offline browsing, which gives you the ability to open the web pages from cache even when you are not connected to the Internet.

So the answer is: yes the "Make avaliable online" option for web pages stores the files on the temporary files folder, and is used as a cache when online.

Other concept is the same option for files and folder, that is stored appart and it's accesible from the explorer, not Internet Explorer.

I've done some tests and the content for Offline Web Pages is stored with temp files, counts for the cache size and gets replaced is the cache limit size is reached.

So I guess there's no chance to protect this content against cache filling.

Cheers,
Dian

 

[cdogg]

No, not quite right. Technically, the files are stored within the temp directory, but they are not part of the cache. When you empty the cache, the offline pages are still available unless you also check the option to "Delete all offline content" as well.

Check this link:

http://www.microsoft.com/Windows/IE/community/columns/favorites.mspx

Once a Web page is selected to be available for offline viewing and the appropriate options have been set, the page will need to be synchronized manually or via a schedule. To synchronize manually, right-click on the favorite you'd like to synchronize, and then select Synchronize...

...Data that is downloaded during synchronization is stored separately to Internet Explorer's cache, and is protected from deletion except for during synchronization or when the separate Delete all offline content option is enabled when deleting temporary Internet files.

So it would appear that as long as you use the Synchronize option, the pages should be safe.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[Diancecht]

Yupp, unless the cache reaches the limit, and those files will be deleted if they're older that the other content. I can assure that because I tested it.

And I also can assure that, working online, they behave as cached files, they're not downloaded from the net unless they've changed.

Cheers,
Dian

 

[cdogg]

Dian,

If I empty my cache and offline content, then visit a page with a lot of mixed content (such as espn.com), the page might take 10-15 seconds to completely load. If I close/reopen the browser afterwards, that same page will load in less than 2 seconds (just long enough for IE to compare changes to what was stored in cache).

So as a test, I cleared all cache again and made this page available offline. The page loads in the same amount of time as it did above on my 2nd visit.


I would have to question how much of a difference it makes to have the page stored in offline files. All the documentation I came across on the net seems to indicate the "sole purpose" of making it available offline is for when you are not connected to the internet (when "work offline" is checked in IE). I've seen no evidence to believe that saving the entire page makes it load faster while you're ONLINE.


Just my final 2¢

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Albert Einstein
[tab][navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[Diancecht]

I did the test using an http sniffer, and the request of items that were previously downloaded as offline content had a 304 reponse (Not Modified).

Are you sure you're synchronizing the page OK? Do you have the same functionality online and offline? Think that not all the content of a web page is avaliable to browse offline.

Cheers,
Dian