I think my previous N81 have around 25MB++ "PHONE MEMORY" on fresh boot.
Now, OVI Maps 2.x and N-Gage Arena will force to install to Phone Memory, which will result to around 5MB++ remaining "Phone Memory".

When my "Phone Memory" is low (less than 1MB?), e.g. internet cache stores on Phone Memory; I will get "Out of Memory, please close some application".
I will then clear the caches and I can run some applications again.
Now, with less than 5MB Phone Memory, if I tried to blast SMS to contact groups, I will get such Out Of Memory error as well.
What I experience is, when my Phone Memory is low, I'm not allow to open applications as well, like Garmin for example or SMS for example. Why is that? This is similar to RAM behaviour or Virtual Memory, but since there is no Virtual Memory in Symbian^1? Or is there?

I don't know how to see RAM for Symbian as I didn't venture onto those apps that can see the details. I'm still confused why Phone Memory will cause lag issue, will cause Out Of Memory error. Even N97 has this issue, if you google around the article, they will talk about this Phone Memory which is low, and a firmware updates increases this Phone Memory.
Thanks, but wouldn't you mind contribute to explain rather than teasing.
I don't mind admit that I am confused and I don't understand this, but will appreciate if you can help me out. Do read my reply above to BBXiong.

N900 is far more simple and straighforward, we can see our internal storage, ram, swap memory, rootfs, etc. clearly unlike Symbian.
Maybe someone can list down in details for Symbian OS, and why does those articles/blogs talk about Phone Memory low instead of RAM? Why does the firmware update on N97 which increases the available Phone Memory helps?

Sorry sir..  You are the only one who know what is NAND RAM..  coz we don't have any knowladge on it.. you are the one who go telling people N900 have NAND RAM...      

we all learning from you...    

Here's something else I wonder:
N97 - 128MB RAM?
After fresh boot, it's around 50MB++ (Phone memory)? Can't remember the exact amount.
N97 Mini - 256MB RAM?
After fresh boot, it has more than 100MB++ (Phone memory).

Why does the RAM affects the Phone Memory available?

What makes out of memory is the little space of phone memory. Hence, huge space = won't be a problem. The speed depend on the RAM and how many application is open. If application is design like auto launcher after booting, alot of RAM will be used thus make the phone terribly lag. Also, it depend on the OS whether the OS is smart enough to maintain the speed by controlling the running app like freezing it on the background.

When installing an application 

So I really think it's Symbian problem, not the hardware. :\

To reduce the seek time when performing phone related operation, perhaps?

I think the seek "thing" doesn't show any huge differences here. Take example like your HDD, you can partitioned it to C:, D:, E:. So phone memory and internal memory is like one "HDD" but separate into 2 types of partition = phone memory and internal memory C:.

Correct me if I'm wrong, just telling what I understand so far

Try N81.....

You never confirm the exact problem for that? Should check RAM level to verify the source of the error.

Well, I dump N97 a long time ago. So don't remember much but only could think that it was when installing an application 

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Added on September 20, 2010, 2:50 pmWhy can't people correct me if they know I was wrong. Damn, all the question seeems forward to me. >.<

BBXiong:
Sorry, I think I may have confused myself. I remember now, there is a different message called "Memory full. Please delete some data and try again".
But somehow it also relate to some error when I tried to run Garmin when my Phone Memory is low, maybe the RAM is also low that time, I'm not sure. Haven't used a Symbian for quite long time already.

Well, I don't really like to argue, so I just answer it, can't meh?

And let the person be. 

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Added on September 20, 2010, 2:57 pmOrait, I'm out from discussion. Need to run some errand

Hehe, thanks for your time and also those that help to explains.

I think someone can list down in details each part and also the error for easier reference or confused people like me.
Example: like what sklchan listed each item and it's explanation
Then the types of error message, like Out Of Memory Or Memory Full, what else?

Many people also confused with Internal/Mass Storage with Phone Memory; It doesn't matter if they get a 16GB model VS 8GB model or SD card model (e.g. the older generation Nokia which have either option only), the low Phone Memory problem is still there.

Don't really know why, that's why I'm wondering why my Phone Memory low also get error, maybe the ram was also low that time; Have to use those app to see the ram usage only know.

Perhaps, some process still not yet clear off in RAM? Not sure...

memory leak... common for all electronic devices...

Its just the limitation for symbian os up to Symbian^3. IIANM, Symbian^4 will allow much higher resolution

better let the wiki answer in detail... 

http://en.wikipedia.org/wiki/Memory_leak

but in small screen does those resolution do any good in text reading? 

well, some rough explaination la..

when an application uses ram, it would need to register the address to the system, and that portion of ram would be allocated for the application only, no other application can access it. Normally, when the application finish using it, it would free the ram from its usage. memory leak is when the application did not free off the ram that is no longer being used by it. Since no other application can access it, the usable ram would become smaller, and the ram taken by the application that is not free would be 'forever' lost...until you restart the device that is...

now getting more and more itu pid pid pad pad... they're test test water with bigger portable devices but it look silly with a "pad" phone