* Crash tolerance
By default it is possible for an abrupt crash (e.g., power failure,
OS kernel panic, or application process crash) to corrupt the gdbm
database file. A new Linux-only mechanism enables applications to
recover the database state corresponding to the most recent
successful gdbm_sync() call before the crash. See the chapter 17
"Crash Tolerance" in the GDBM manual.
* New database file format: numsync
The new "numsync" database format is designed to better support
crash tolerance. To create a database in numsync format, the gdbm_open
(or gdbm_fd_open) function must be given the GDBM_NEWDB|GDBM_NUMSYNC
flags. The GDBM_NUMSYNC flag also takes effect when used together
with GDBM_WRCREAT, provided that the new file is created.
New function gdbm_convert() is provided for converting the databases
from standard GDBM format to numsync and vice versa.
The gdbmtool tool can also be used for converting databases between
these two formats.
* Changes in gdbmtool
** Fix string output in non-ASCII encodings
Printable multi-byte sequences are correctly represented on output.
This also fixes octal representation of unprintable characters.
** The filename variable
This variable supplies the name of database file for use in "open"
command, if the latter is called without arguments. If "open" is
called with the file name argument, the "filename" variable is
initialized to this value.
** The fd variable
If set, its value must be an open file descriptor referring to a
GDBM database file. The "open" command will use gdbm_fd_open
function to use this file. Upon closing the database, this
descriptor will be closed and the variable will be unset.
The file descriptor to use can also be supplied using the
-d (--db-descriptor) command line option.
** The format variable
Defines the format in which new databases will be created. Allowed
values are: "standard" (default) and "numsync".
** New commands: upgrade and downgrade
The "upgrade" command converts current database to the numsync
(extended) format. The "downgrade" command converts current database
to the standard format.
** New command: snapshot
The "snapshot" command is part of the new crash tolerance support.
Given the names of two snapshot files, it analyzes them and selects
the one to be used for database recovery. See the GDBM manual,
section 17.5 "Manual crash recovery" for a detailed discussion of its