When I am using the AUI, I get an error message similar to

AUI Error
Write to temporary database file was unsuccessful. 539016 bytes at record 278479703, record length = 32 bytes.

What does this mean?

Answer:

The AUI tried to create a temporary database file that could not fit in the free disk space. In the above example, the size of the temporary database file before the write was

record 278479703 * 32 bytes/record * 1 GB/(2**30 bytes) = 8.3 GB.

The free disk space, not including the temporary database file, was 8.3 GB, so the next write to the temporary database file would have overflowed free disk space.