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=item C<xxxxxx.LKl>*

Sorted Link file (short terms)

=item C<xxxxxx.LK2>*

Sorted Link file (long terms)

=item C<xxxxxx.BKP>

Master file backup

=item C<xxxxxx.XHF>

Hit file index

=item C<xxxxxx.HIT>

Hit file

=item C<xxxxxx.SRT>*

lib/Biblio/Isis/Manual.pod  view on Meta::CPAN

=item C<NXTMFP>

Offset to next available position in last block

=item C<MFTYPE>

always 0 for user data base file (1 for system message files)

=back

(the last four fields are used for statistics during backup/restore).

=head2 C. Master file block format

The Master file records are stored consecutively, one after the other,
each record occupying exactly C<MFRL> bytes. The file is stored as
physical blocks of 512 bytes. A record may begin at any word boundary
between 0-498 (no record begins between 500-510) and may span over two
or more blocks.

As the Master file is created and/or updated, the system maintains an

lib/Biblio/Isis/Manual.pod  view on Meta::CPAN

On C<MST> C<STATUS> is set to 1

=head2 F. Master file reorganization

As indicated above, as Master file records are updated the C<MST> file
grows in size and there will be lost space in the file which cannot be
used. The reorganization facilities allow this space to be reclaimed by
recompacting the file.

During the backup phase a Master file backup file is created (C<.BKP>).
The structure and format of this file is the same as the Master file
(C<.MST>), except that a Crossreference file is not required as all the
records are adjacent. Records marked for deletion are not backed up.
Because only the latest copy of each record is backed up, the system
does not allow you to perform a backup whenever an Inverted file update
is pending for one or more records.

During the restore phase the backup file is read sequentially and the
program recreates the C<MST> and C<XRF> file. At this point alt records which
were marked for logical deletion (before the backup) are now marked as
physically deleted (by setting C<XRFMFB = -1> and C<XRFMFP = 0>.
Deleted records are detected by checking holes in the C<MFN> numbering.

=head1 Inverted file structure and record formats

=head2 A. Introduction

The CDS/ISIS Inverted file consists of six physical files, five of
which contain the dictionary of searchable terms (organized as a
B*tree) and the sixth contains the list of postings associated with