+.PP
+See
+\fBamanda-changers\fR(7)
+for more information on configuring changers\&.
+.SH "DUMP SPLITTING CONFIGURATION"
+.PP
+Amanda can "split" dumps into parts while writing them to storage media\&. This allows Amanda to recover gracefully from a failure while writing a part to a volume, by simply selecting a new volume and re\-writing the dump from the beginning of the failed part\&. Parts also allow Amanda to seek directly to the required data, although this functionality is not yet used\&.
+.PP
+In order to support re\-writing from the beginning of a failed part, Amanda must have access to the contents of the part after it has been partially written\&. If the dump is being read from holding disk, then the part contents are availble there\&. Otherwise, the part must be cached, and this can be done memory or on disk\&. In either of the latter cases, the cache must have enough space to hold an entire part\&.
+.PP
+Because it is common for a single Amanda configuration to use both holding\-disk (FILE\-WRITE) and direct (known as PORT\-WRITE) dumps, Amanda allows the configuration of different split sizes for the two cases\&. This allows, for example, for a part size appropriate to large tapes when performing FILE\-WRITE dumps, with a part size limited by available disk or memory when performing PORT\-WRITE dumps\&.
+.PP
+Selecting a proper split size is a delicate matter\&. If the parts are too large, substantial storage space may be wasted in failed parts\&. If too small, large dumps will be split into innumerable tiny dumpfiles, adding to restoration complexity; furthermore, an excess of filemarks will cause slower tape drive operation and reduce the usable space on tape\&. A good rule of thumb is 1/10 of the size of a volume of storage media\&.
+.PP
+In versions of Amanda through 3\&.1\&.*, splitting was controlled by the dumptype parameters
+\fBtape\-splitsize\fR,
+\fBsplit\-diskbuffer\fR, and
+\fBfallback\-splitsize\fR\&. These keywords had confusing and non\-intuitive interactions, and have since been deprecated\&.
+.PP
+If the deprecated keywords are not present, subsequent versions of Amanda use the dumptype parameter
+\fBallow\-split\fR
+to control whether a DLE can be split, and the
+\fItapetype\fR
+parameters
+\fBpart\-size\fR,
+\fBpart\-cache\-type\fR,
+\fBpart\-cache\-dir\fR, and
+\fBpart\-cache\-max\-size\fR\&. The
+\fBpart\-size\fR
+specifies the "normal" part size, while the
+\fBpart\-cache\-*\fR
+parameters describe how to behave when caching is required (on PORT\-WRITE)\&. Full details on these parameters are given above\&.