Title: TDB with 64-bit and 32-bit JVMs

TDB runs on both 32-bit and 64-bit Java Virtual Machines. The same
file formats are used on both systems and database files can be
transferred between architectures (no TDB system should be running
for the the database at the time of copy). What differs is the file
access mechanism used.

The file access mechanism can be set explicitly, but this is not a
good idea for production usage, only for experimentation - see the
[File Access mode option](configuration.html#file_access_mode).

## 64-bit Java

On 64-bit Java, TDB uses memory mapped files and the operating
system handles much of the caching between RAM and disk. The amount
of RAM used for file caching increases and decreases as other
application run on the machine. The fewer other programs running on
the machine, the more RAM will be available for file caching.

TDB is faster on a 64 bit JVM because more memory is available for
file caching.

## 32-bit Java

On 32-bit Java, TDB uses it's own file caching to enable large
databases. 32-bit Java limits the address space of the JVM to about
1.5Gbytes (the exact size is JVM-dependent), and this includes
memory mapped files, even though they are not in the Java heap. The
JVM heap size may need to be increased to make space for the disk
caches used by TDB.