|The Pliant database server is expected to recover gracefully in case of
a process crash.
So, basically, the content of the database is, at any time, a set of
instructions specifying the content of the database, plus a set of instructions
specifying changes since the last write of the overall content.
When the database contains a permament log file, the set of instructions
specifying the last changes is written in the log file, so in order to
know where to find these in case of crash, we write a 'precovery' instruction
at the end of the main database file, specifying the offset we have to read
from in the log file.
If you had no permanent log file in your database, there would be no
'precovery' instruction in the main file: changes would simply be appended,
until the file is completely rewritten.