Oracle on 64bit UX vs 32bit Windows

[Ravi_8]

Hi,

The number of instances that you can run on Windows is less (2-3), whereas in Unix you can create instances as long as you have enough memory and swap

[Wodisch]

to add to ravi's point:
handling of multiple instances on windows is difficult, as "they" tend to use the registry for the one-and-only SID, so in case of multiple ones, you have to work around that.
Of course you could use variables like on UNIX, it's just not the "M$-way-of-life" and hence you won't find information about doing it the "UNIX-way"...
:-(

[Julio Yamawaki]

Hi,

Today I was navigating in Oracle's Metalink and I found some interesting news:
1. It's possible to have an instance with 4 GB total (processes + SGA). I just don't know if it's is reliable or not because I have never used.
2. In UNIX, you have a total of shared memory divided by all instances, i.e., if you have 2 GB of shared memory, all instances will share the same space
3. In Windows, you can have as many instances as you have free memory (probably you will have problem with processor, disk, etc.), each one of up to 4 GB
4. In Windows it's more difficult to find problem in startup and shutdown, services just doesn't show the problem if the instance doesn't start, in UNIX you have a more visual interface. We have one instance in Windows and when we have problem, we have to start the instance manually, like in UNIX.
5. It seem that in UNIX Oracle have a more powerful performance. Certainly, UNIX box have a more powerfull I/O bus and Oracle in UNIX is used when you have a large number of users. I don't know such a Oracle installation in Windows with more than 50 users (I don't know, but it may exist).

[Bill Hassell]

A 64bit OS doersn't offer many advantages to a simple 32bit program. The memory management for 32bit apps works like this: 960 megs for the largest data area inside the program and the same for a shared memory area. By choosing other link options, the executable can ask for as much as 1750 megs for data and/or shared memory.

However, the shared memory area (SGA in Oracle) may be shared by every process in the system. Memory mapped files, shared libraries, other shared memory segments, all are placed in a single map...so a single Oracle instance *might* get 800 megs (1200-1500 is the Oracle executables are relinked), but multiple (32bit) Oracle instances must share the same single memory map.

Now the 64bit OS begins to help the crippled 32bit Oracle app. By using memory windows, a single instance (or multiple instances) can have an unfragmented window of 1750 megs for shared memory. The 64bit OS can handle dozens of gigabytes of RAM while running the 32bit applications.

Note that Oracle 64bit removes all the quirky limitations of a 32bit app. In that case, shared memory is limited to 8Tb (8,000 Gb) and HP-UX will handle these ultra-large programs with no problem.

As far as threaded apps on HP-UX, they work very well as long as you have multiple processors and HP-UX scales dozens of processors without effort.