So just what is this phone cache thing anyway?

Being the nerd that I am, I'm often confronted with questions from the family - not news really, but just pretty much par for the course for anyone who "does computers" for a living.

The most recent question from a family member was this:

"Many of my phone apps have a "clear cache" tab. What happens when you do this? Does it decrease the storage amount on my phone? I get a low storage amount notice on my phone."

As this has no simple answer, I figured I'd write it up properly for all to share.

What is cache?

Cache, in this context, is just a chunk of memory storage in your computer.  The purpose of all kinds of cache is to make things run faster.  There are different kinds of cache.  In this case, the cache in your smartphone is used simply to display things faster instead of having to go out to the network and download them again.

For example - most every time you visit your computers home page, you are confronted with the logo on that page - be it Google, or Yahoo, AOL, Etc.  Now that logo doesn't change too often in most cases - and that logo took your phone or computer a few seconds to go out and download and then display it.  This same speedup applies to the map app, and the weather app, and so forth.

Where is it used, and network loads...

Now if you're at your desktop computer and you're connected via wireless to the Internet using a fast ISP, the few seconds it takes to load that logo doesn't matter.  Still though, your computer has massive amounts of storage and caches TONS of files.

Now on your smartphone, even with the latest LTE networks and all that jazz, it STILL will take a few seconds to download that image - and as it almost never changes, there's no good reason to download it EVERY TIME you visit the page.  This extra network load can cost a cellular company MILLIONS of dollars and it's a TOTAL WASTE of the company's bandwidth to re-download a logo for each and every smartphone out there.  Also, many carriers will charge you for using up your data in your plan too - and they LOVE to charge us.

So instead of wasting your time and money and your cellular carriers' money and bandwidth every time you hit the page, your phone keeps a copy of that image in it's cache.  Any program on your smartphone that talks to the Internet - that includes the "weather app", reading your mail, updating your calendar, Etc. can all have their own local cache of files that they need to download and display.  Using this cache makes your phone look faster because it doesn't have to take a few seconds to show you the logo, or the weather conditions, or whatever - because the pretty picture is already there in the cache - and all it needs to do is go out and make sure it should show you the right one.

The Network Data Plan and Cache Clearing

One other thing - many Android users do not have a grandfathered unlimited AT&T data plan like I have, or they're not on Cricket (remember, I work for them and we do unlimited everything on our phones - data, minutes, texting) - but for those of you who are on Verizon, or a newer AT&T data plan, Sprint or T-Mobile - then you're paying a pricey premium for every Internet bit you get - and are getting charged for going over planned data.

Now in reality, most users won't get near the 4gb limit on their data plans - I mean, I've gotten close - 3.8 gigs - but that's me watching Archer on Netflix, over wireless, in traffic, on my iPhone - this is common during the colder months where my commute can become an hour at 15mph.  (Yes, I'm one of THOSE people who watch TV and drive...) but the fact is, most folks don't have a 4 gig plan or use Cricket - they have a 2 gig plan - or maybe less - and going over could mean a $10, $20 or $50 overcharge surprise in your next bill.

Also, clearing your cache will not always speed things up - I mean, if you clear the cache in the Map app, then yes, the camera might run faster afterwards because it can use all that map space for pictures - but clearing the Map app cache will make the Map app slower - because the maps it already has locally stored will have to be re-downloaded over the wireless data plan again.

So what about those Low Storage notices on my phone?

First, a word about storage...

Smartphones and desktop computers have a lot in common - they both are computers, they both have RAM and they both have non-volatile storage.

Non-Volatile Storage is the term that refers to where your data is kept.  If you use a PC at home, then there's a hard disk that stores your programs and files and such.  If you use a newer computer, like say a MacBook Air, then your hard disk might have been replaced with a flash disk.  In these cases, when the computer is off, the hard disk or flash "disk" are keeping your data safe.

Don't confuse RAM with storage - the RAM in a computer determines how much work the computer can do at one time - the more RAM, the more it can juggle smoothly.  Computers without enough RAM can't do as much - and when things get bad, they start swapping RAM with storage - and then your computer starts working really slowly.  And putting programs and data from RAM into a spinning disk takes lots of time..

Now Smartphones don't have spinning hard disks - they do have flash memory though - and flash memory is fast, and depending on the device, it can be very abundant, depending on your device and how it's setup.

Second, lets talk about how strorage is used on phones..

Users of iPhones will only very rarely see messages like the ones you are getting off your droid - this is because iPhones come with 8gigs, 16gigs, 32gigs or 64gigs of flash storage built into them.  It all depends on how much you pay for the phone.  When users of these devices dock their phones, the iTunes program works with them, backs the phone up, and permits folks to control what programs are installed, and what pictures are taking space, what songs are stored in it, and movies, and so forth.

On other smartphones - like android phones, storage isn't so simply handled as it is in the Apple products  - there's no "droid-tunes app" to help organize the storage in your droids.

Fortunately android-based smartphones come with an additional memory slot in them, but only come with a tiny amount of memory in the phone itself.  Newer, bigger droids - like the Huawei Mercury from Cricket (an awesome droid if I don't say so myself) comes with 4gigs of storage - and this is common among all the high-end android phones out there from other carriers - you can expect to pay upwards of $150+ for phones with this kind of built in flash storage.

The earlier generation of android phones come with even less storage built in - my original Huawei Ascend only came with 1.2 gigs of usable storage.  Now this sounds like a lot, but once you start syncing your email, browsing the web, running the weather app, and otherwise using the phone and installing additional apps, this 1.2 gigs of usable storage fills up fast - and don't take any photos...

The pictures are a huge deficit to these phones - note that all the photos you take will pour into this little space as well - and with the high-end cameras these phones have - you only get 40-80 pictures at 8 megapixels and then you'll be getting these messages too!

Fortunately, Google saw this limitation in their design, and all droids come with one or more memory slots.  Using this memory slot is recommended as you can put programs, data, pictures, music and even movies into a nice little memory card - and once that's done, you'll be all set.

I would recommend finding out what kind of memory your phone uses for this - most (maybe all) take something called MicroSD memory - and many phones actually come with MicroSD memory cards - but usually those cards are tiny - sometimes as small as 1 gig - and that's not much given the amount of data these smartphones use and create.

Getting more memory for your phone...

On Amazon I was able to find a 16gb MicroSD HC card - plenty large enough for most users to store hours of music, hundreds of photos, 5000 books and probably as many apps for only $13.

Not all phones can use a card that big - it's important to look up your phones specs and find out how much it can handle before shopping for upgrades.  If you've got an older android phone, you might find out that it can't handle more than 8 gigs of additional flash memory - and that would be unpleasant if you bought a 16 gig card that you couldn't use.

Just do some google searches on your phones model with the word "specs" in the search - and somewhere you'll find out what the maximum additional memory is.

Now it's just not as simple as plugging the memory in either - if your phone doesn't already have additional memory then you can simply run down the Best Buy, grab some and stuff it into the phone - and then many programs will see the open space and take advantage of it.

The tricky part comes in when you already have a small memory stick in your phone - because you'll have to back up the contents of that memory stick on your computer, then swap the memory cards, then re-upload all the old data (if you want it).

Many apps might then need to be told where to put their files - and if told to use the SD card, they'll store commonly used stuff there - and the phone will run faster, be happier, Etc.

Not all memory cards are the same - and yes, there are some REALLY cheap memory cards out there - but just because the memory card is cheap and large, that doesn't make it better.  Remember the first time someone (like me) said that you need to upgrade the memory in your computer?  Well, this flash memory stuff isn't all the same either - flash memory comes in different "classes" as well - so when you're buying that 8gb or 16gb memory card, be sure to look for things that indicate the speed of the flash memory itself.  Remember that flash memory in your phone is stuff that you'll be using - so you want it to be fast.

Flash memory "classes" are numbered for the speed of the memory - Class 2, Class 4, Class 6, Class 10, Etc.  The higher "class" a flash memory is, the more expensive it will be - and the faster it will be.  Note that not all phones will be able to go as fast as the fastest class memory out there - so if you paid and extra $40 for that Class 10 SDHC 32gb card (if you phone can handle it at all) don't be disappointed if your phone doesn't appear any faster.  When you upgrade your phone next and move that huge memory card over, the next phone might be able to get more out of it.

For most of us out there, Class 6 performs well enough, and most of the tech out there will use it just fine - and the price point is just right.  If you're seriously into photography, the Class 10 will be worth it in time saved - but this class of memory is overkill for probably all the phones out there right now.

Cleaning up your phone's storage

Now this is an area that I'm not experienced enough in with Androids - either the apps themselves, or perhaps the OS, determines where best to store things - and given the variety of phones out there, it might be different per phone, or different on different versions of the Android OS.

In any case, once you have the space available, using it is the next step.  The first thing I'd recommend you do is start my looking at where your photos live, and getting them out of the phones memory - and then focus on the music if you have that on there.  Those two alone should free up enough space to make sure that nothing complains.

On Android phones, go into the menu, choose Settings, Applications - then you can tell the phone where applications should live.  By moving applications into the SD card, you remove them from your phones built-in memory and make the phone faster.

Ideally, commonly used applications should live in the phones memory - like your mail client and web browser.  The phone's own OS might prevent you moving of these apps as well - some apps just can't live on the SD card because the phone would break if you docked or unplugged the card.

If an app supports the ability to use SD card memory for itself, the options to utilize the SD card will be found in this menu as well.

It's not as elegant as Apple's solution to the problem, but the Android memory management scheme does work, once you know where it lives.

Cheers!