If a Texinfo file has more than 30,000 bytes,
texinfo-format-buffer automatically creates a tag table
for its Info file; makeinfo always creates a tag table. With
a tag table, Info can jump to new nodes more quickly than it can
otherwise.
In addition, if the Texinfo file contains more than about 70,000
bytes, texinfo-format-buffer and makeinfo split the
large Info file into shorter indirect subfiles of about 50,000
bytes each. Big files are split into smaller files so that Emacs does
not need to make a large buffer to hold the whole of a large Info
file; instead, Emacs allocates just enough memory for the small, split-off
file that is needed at the time. This way, Emacs avoids wasting
memory when you run Info. (Before splitting was implemented, Info
files were always kept short and include files were designed as
a way to create a single, large printed manual out of the smaller Info
files. See Include Files, for more information. Include files are
still used for very large documents, such as The Emacs Lisp
Reference Manual, in which each chapter is a separate file.)
When a file is split, Info itself makes use of a shortened version of the original file that contains just the tag table and references to the files that were split off. The split-off files are called indirect files.
The split-off files have names that are created by appending -1,
-2, -3 and so on to the file name specified by the
@setfilename command. The shortened version of the original file
continues to have the name specified by @setfilename.
At one stage in writing this document, for example, the Info file was saved
as the file test-texinfo and that file looked like this:
Info file: test-texinfo, -*-Text-*-
produced by texinfo-format-buffer
from file: new-texinfo-manual.texinfo
^_
Indirect:
test-texinfo-1: 102
test-texinfo-2: 50422
test-texinfo-3: 101300
^_^L
Tag table:
(Indirect)
Node: overview^?104
Node: info file^?1271
Node: printed manual^?4853
Node: conventions^?6855
...
(But test-texinfo had far more nodes than are shown here.) Each of
the split-off, indirect files, test-texinfo-1,
test-texinfo-2, and test-texinfo-3, is listed in this file
after the line that says Indirect:. The tag table is listed after
the line that says Tag table:.
In the list of indirect files, the number following the file name records the cumulative number of bytes in the preceding indirect files, not counting the file list itself, the tag table, or the permissions text in each file. In the tag table, the number following the node name records the location of the beginning of the node, in bytes from the beginning of the (unsplit) output.
If you are using texinfo-format-buffer to create Info files,
you may want to run the Info-validate command. (The
makeinfo command does such a good job on its own, you do not
need Info-validate.) However, you cannot run the M-x
Info-validate node-checking command on indirect files. For
information on how to prevent files from being split and how to
validate the structure of the nodes, see Using Info-validate.