Depends SDE 32-bit/ 64-bit on the OS or on the RDBMS?

SebastianKrings

Hi,

I have a 64-bit operating system.
I do not know wether RDBMS (MS SQL Server) will be 32-bit or 64-bit.
When installing the Arc SDE need I install 64-bit because of the OS or will this depend on the RDBMS (wether this is 32-bit or 64-bit).

Or does this not matter and I am absolutely free to install SDE in 32-bit or 64-bit. What about the compatibility to OS and RDBMS, seen from bottom-up (SDE 32-bit while OS and/or RDBMS are 64-bit) or top-down (SDE 64-bit while OS and/ or RDBMS are 32-bit).

Thanks.

VinceAngelo

The operating system only matters if it restricts you from making a choice -- If the OS is 32-bit
you can *only* use 32-bit RDBMS and 32-bit ArcSDE.

If the OS is 64-bit then you can choose the bit size of the database.  Contrary to popular notions,
databases are unlikely to be significantly impacted by application word size -- the performance
of a database is keyed to I/O subsystem performance.  In many ways, 64-bit RDBMSes are
larger and slower than 32-bit (the executables are nearly twice as large) but the one advantage
they have is in memory addressing -- a 64-bit application is more likely to be able to use very
large RAM caches (>4Gb), but even the the need for this is dictated by the RAM avaliable, and
the number of instances (4 instances on 16Gb system wouldn't let you effectively use more than
~3Gb each effectively anyway, since you need to reserve at least 2-3Gb to the OS)

*Then* you come to the ArcSDE application.  Again, contrary to popular conceptions, there is
not always a significant performance benefit to having a 64-bit ArcSDE -- in fact, the last time I
tested (with 9.2sp4), 32-bit ArcSDE actually performed *faster* than 64-bit ArcSDE on a Windows
host, probably because the instructions were smaller. 

But there is an additional variable (which you have not mentioned):  Which version of ArcGIS you
are using.  ArcGIS Server 10.1 is a 64-bit application (only), while 10.0 and earlier are 32-bit (only).
In order to run a 64-bit RDBMS with a 32-bit application, you must install a 32-bit client (DLLs are
NOT interoperable).  If you're using Direct Connect with ArcGIS Server on the database host, then
you need the right client library binaries.  In many ways, it's easiest to match the ArcSDE install
to the application word size of the other ArcGIS components on the same system -- If you run
AGS on a different host, or only have Desktop clients on other hosts, then matching the RDBMS
application wordsize is a natural choice.

Since you are using SQL-Server, you don't face the further complication for Oracle users -- Oracle
client libraries are *huge*.  ArcGIS 10.0 users (and before) required a 400-600Mb 32-bit client
library in addition to the 3-4Gb 64-bit application.  ArcGIS 10.1 starts to support the Instant Client
which is much lighter weight, so there may be room on older disks for Direct Connect libraries.

If you have the time, I recommend you benchmark the performance of the various components on
your own hardware, since the actual performance is bound by the system on which it operates.

- V