1 <chapter id="administration">
2 <!-- $Id: administration.xml,v 1.9 2002-10-17 08:10:08 mike Exp $ -->
3 <title>Administrating Zebra</title>
4 <!-- ### It's a bit daft that this chapter (which describes half of
5 the configuration-file formats) is separated from
6 "recordmodel.xml" (which describes the other half) by the
7 instructions on running zebraidx and zebrasrv. Some careful
8 re-ordering is required here.
12 Unlike many simpler retrieval systems, Zebra supports safe, incremental
13 updates to an existing index.
17 Normally, when Zebra modifies the index it reads a number of records
19 Depending on your specifications and on the contents of each record
20 one the following events take place for each record:
27 The record is indexed as if it never occurred before.
28 Either the Zebra system doesn't know how to identify the record or
29 Zebra can identify the record but didn't find it to be already indexed.
37 The record has already been indexed.
38 In this case either the contents of the record or the location
39 (file) of the record indicates that it has been indexed before.
47 The record is deleted from the index. As in the
48 update-case it must be able to identify the record.
56 Please note that in both the modify- and delete- case the Zebra
57 indexer must be able to generate a unique key that identifies the record
58 in question (more on this below).
62 To administrate the Zebra retrieval system, you run the
63 <literal>zebraidx</literal> program.
64 This program supports a number of options which are preceded by a dash,
65 and a few commands (not preceded by dash).
69 Both the Zebra administrative tool and the Z39.50 server share a
70 set of index files and a global configuration file.
71 The name of the configuration file defaults to
72 <literal>zebra.cfg</literal>.
73 The configuration file includes specifications on how to index
74 various kinds of records and where the other configuration files
75 are located. <literal>zebrasrv</literal> and <literal>zebraidx</literal>
76 <emphasis>must</emphasis> be run in the directory where the
77 configuration file lives unless you indicate the location of the
78 configuration file by option <literal>-c</literal>.
81 <sect1 id="record-types">
82 <title>Record Types</title>
85 Indexing is a per-record process, in which either insert/modify/delete
86 will occur. Before a record is indexed search keys are extracted from
87 whatever might be the layout the original record (sgml,html,text, etc..).
88 The Zebra system currently supports two fundamental types of records:
89 structured and simple text.
90 To specify a particular extraction process, use either the
91 command line option <literal>-t</literal> or specify a
92 <literal>recordType</literal> setting in the configuration file.
97 <sect1 id="configuration-file">
98 <title>The Zebra Configuration File</title>
101 The Zebra configuration file, read by <literal>zebraidx</literal> and
102 <literal>zebrasrv</literal> defaults to <literal>zebra.cfg</literal>
103 unless specified by <literal>-c</literal> option.
107 You can edit the configuration file with a normal text editor.
108 parameter names and values are separated by colons in the file. Lines
109 starting with a hash sign (<literal>#</literal>) are
114 If you manage different sets of records that share common
115 characteristics, you can organize the configuration settings for each
117 When <literal>zebraidx</literal> is run and you wish to address a
118 given group you specify the group name with the <literal>-g</literal>
120 In this case settings that have the group name as their prefix
121 will be used by <literal>zebraidx</literal>.
122 If no <literal>-g</literal> option is specified, the settings
123 without prefix are used.
127 In the configuration file, the group name is placed before the option
128 name itself, separated by a dot (.). For instance, to set the record type
129 for group <literal>public</literal> to <literal>grs.sgml</literal>
130 (the SGML-like format for structured records) you would write:
135 public.recordType: grs.sgml
140 To set the default value of the record type to <literal>text</literal>
151 The available configuration settings are summarized below. They will be
152 explained further in the following sections.
156 FIXME - Didn't Adam make something to have multiple databases in multiple dirs...
164 <emphasis>group</emphasis>
165 .recordType[<emphasis>.name</emphasis>]:
166 <replaceable>type</replaceable>
170 Specifies how records with the file extension
171 <emphasis>name</emphasis> should be handled by the indexer.
172 This option may also be specified as a command line option
173 (<literal>-t</literal>). Note that if you do not specify a
174 <emphasis>name</emphasis>, the setting applies to all files.
175 In general, the record type specifier consists of the elements (each
176 element separated by dot), <emphasis>fundamental-type</emphasis>,
177 <emphasis>file-read-type</emphasis> and arguments. Currently, two
178 fundamental types exist, <literal>text</literal> and
179 <literal>grs</literal>.
184 <term><emphasis>group</emphasis>.recordId:
185 <replaceable>record-id-spec</replaceable></term>
188 Specifies how the records are to be identified when updated. See
189 <xref linkend="locating-records"/>.
194 <term><emphasis>group</emphasis>.database:
195 <replaceable>database</replaceable></term>
198 Specifies the Z39.50 database name.
199 <!-- FIXME - now we can have multiple databases in one server. -H -->
204 <term><emphasis>group</emphasis>.storeKeys:
205 <replaceable>boolean</replaceable></term>
208 Specifies whether key information should be saved for a given
209 group of records. If you plan to update/delete this type of
210 records later this should be specified as 1; otherwise it
211 should be 0 (default), to save register space.
212 <!-- ### this is the first mention of "register" -->
213 See <xref linkend="file-ids"/>.
218 <term><emphasis>group</emphasis>.storeData:
219 <replaceable>boolean</replaceable></term>
222 Specifies whether the records should be stored internally
223 in the Zebra system files.
224 If you want to maintain the raw records yourself,
225 this option should be false (0).
226 If you want Zebra to take care of the records for you, it
232 <!-- ### probably a better place to define "register" -->
233 <term>register: <replaceable>register-location</replaceable></term>
236 Specifies the location of the various register files that Zebra uses
237 to represent your databases.
238 See <xref linkend="register-location"/>.
243 <term>shadow: <replaceable>register-location</replaceable></term>
246 Enables the <emphasis>safe update</emphasis> facility of Zebra, and
247 tells the system where to place the required, temporary files.
248 See <xref linkend="shadow-registers"/>.
253 <term>lockDir: <replaceable>directory</replaceable></term>
256 Directory in which various lock files are stored.
261 <term>keyTmpDir: <replaceable>directory</replaceable></term>
264 Directory in which temporary files used during zebraidx's update
270 <term>setTmpDir: <replaceable>directory</replaceable></term>
273 Specifies the directory that the server uses for temporary result sets.
274 If not specified <literal>/tmp</literal> will be used.
279 <term>profilePath: <literal>path</literal></term>
282 Specifies a path of profile specification files.
283 The path is composed of one or more directories separated by
284 colon. Similar to PATH for UNIX systems.
289 <term>attset: <replaceable>filename</replaceable></term>
292 Specifies the filename(s) of attribute set files for use in
293 searching. At least the Bib-1 set should be loaded
294 (<literal>bib1.att</literal>).
295 The <literal>profilePath</literal> setting is used to look for
297 See <xref linkend="attset-files"/>
302 <term>memMax: <replaceable>size</replaceable></term>
305 Specifies <replaceable>size</replaceable> of internal memory
306 to use for the zebraidx program.
307 The amount is given in megabytes - default is 4 (4 MB).
313 <term>root: <replaceable>dir</replaceable></term>
316 Specifies a directory base for Zebra. All relative paths
317 given (in profilePath, register, shadow) are based on this
318 directory. This setting is useful if if you Zebra server
319 is running in a different directory from where
320 <literal>zebra.cfg</literal> is located.
330 <sect1 id="locating-records">
331 <title>Locating Records</title>
334 The default behavior of the Zebra system is to reference the
335 records from their original location, i.e. where they were found when you
336 ran <literal>zebraidx</literal>.
337 That is, when a client wishes to retrieve a record
338 following a search operation, the files are accessed from the place
339 where you originally put them - if you remove the files (without
340 running <literal>zebraidx</literal> again, the server will return
341 diagnostic number 14 (``System error in presenting records'') to
346 If your input files are not permanent - for example if you retrieve
347 your records from an outside source, or if they were temporarily
348 mounted on a CD-ROM drive,
349 you may want Zebra to make an internal copy of them. To do this,
350 you specify 1 (true) in the <literal>storeData</literal> setting. When
351 the Z39.50 server retrieves the records they will be read from the
352 internal file structures of the system.
357 <sect1 id="simple-indexing">
358 <title>Indexing with no Record IDs (Simple Indexing)</title>
361 If you have a set of records that are not expected to change over time
362 you may can build your database without record IDs.
363 This indexing method uses less space than the other methods and
368 To use this method, you simply omit the <literal>recordId</literal> entry
369 for the group of files that you index. To add a set of records you use
370 <literal>zebraidx</literal> with the <literal>update</literal> command. The
371 <literal>update</literal> command will always add all of the records that it
372 encounters to the index - whether they have already been indexed or
373 not. If the set of indexed files change, you should delete all of the
374 index files, and build a new index from scratch.
378 Consider a system in which you have a group of text files called
379 <literal>simple</literal>.
380 That group of records should belong to a Z39.50 database called
381 <literal>textbase</literal>.
382 The following <literal>zebra.cfg</literal> file will suffice:
387 profilePath: /usr/local/yaz
389 simple.recordType: text
390 simple.database: textbase
396 Since the existing records in an index can not be addressed by their
397 IDs, it is impossible to delete or modify records when using this method.
402 <sect1 id="file-ids">
403 <title>Indexing with File Record IDs</title>
406 If you have a set of files that regularly change over time: Old files
407 are deleted, new ones are added, or existing files are modified, you
408 can benefit from using the <emphasis>file ID</emphasis>
409 indexing methodology.
410 Examples of this type of database might include an index of WWW
411 resources, or a USENET news spool area.
412 Briefly speaking, the file key methodology uses the directory paths
413 of the individual records as a unique identifier for each record.
414 To perform indexing of a directory with file keys, again, you specify
415 the top-level directory after the <literal>update</literal> command.
416 The command will recursively traverse the directories and compare
417 each one with whatever have been indexed before in that same directory.
418 If a file is new (not in the previous version of the directory) it
419 is inserted into the registers; if a file was already indexed and
420 it has been modified since the last update, the index is also
421 modified; if a file has been removed since the last
422 visit, it is deleted from the index.
426 The resulting system is easy to administrate. To delete a record you
427 simply have to delete the corresponding file (say, with the
428 <literal>rm</literal> command). And to add records you create new
429 files (or directories with files). For your changes to take effect
430 in the register you must run <literal>zebraidx update</literal> with
431 the same directory root again. This mode of operation requires more
432 disk space than simpler indexing methods, but it makes it easier for
433 you to keep the index in sync with a frequently changing set of data.
434 If you combine this system with the <emphasis>safe update</emphasis>
435 facility (see below), you never have to take your server off-line for
436 maintenance or register updating purposes.
440 To enable indexing with pathname IDs, you must specify
441 <literal>file</literal> as the value of <literal>recordId</literal>
442 in the configuration file. In addition, you should set
443 <literal>storeKeys</literal> to <literal>1</literal>, since the Zebra
444 indexer must save additional information about the contents of each record
445 in order to modify the indexes correctly at a later time.
449 FIXME - There must be a simpler way to do this with Adams string tags -H
453 For example, to update records of group <literal>esdd</literal>
455 <literal>/data1/records/</literal> you should type:
457 $ zebraidx -g esdd update /data1/records
462 The corresponding configuration file includes:
465 esdd.recordType: grs.sgml
471 <para>You cannot start out with a group of records with simple
472 indexing (no record IDs as in the previous section) and then later
473 enable file record Ids. Zebra must know from the first time that you
475 the files should be indexed with file record IDs.
480 You cannot explicitly delete records when using this method (using the
481 <literal>delete</literal> command to <literal>zebraidx</literal>. Instead
482 you have to delete the files from the file system (or move them to a
484 and then run <literal>zebraidx</literal> with the
485 <literal>update</literal> command.
489 <sect1 id="generic-ids">
490 <title>Indexing with General Record IDs</title>
493 When using this method you construct an (almost) arbitrary, internal
494 record key based on the contents of the record itself and other system
495 information. If you have a group of records that explicitly associates
496 an ID with each record, this method is convenient. For example, the
497 record format may contain a title or a ID-number - unique within the group.
498 In either case you specify the Z39.50 attribute set and use-attribute
499 location in which this information is stored, and the system looks at
500 that field to determine the identity of the record.
504 As before, the record ID is defined by the <literal>recordId</literal>
505 setting in the configuration file. The value of the record ID specification
506 consists of one or more tokens separated by whitespace. The resulting
507 ID is represented in the index by concatenating the tokens and
508 separating them by ASCII value (1).
512 There are three kinds of tokens:
516 <term>Internal record info</term>
519 The token refers to a key that is
520 extracted from the record. The syntax of this token is
521 <literal>(</literal> <emphasis>set</emphasis> <literal>,</literal>
522 <emphasis>use</emphasis> <literal>)</literal>,
523 where <emphasis>set</emphasis> is the
524 attribute set name <emphasis>use</emphasis> is the
525 name or value of the attribute.
530 <term>System variable</term>
533 The system variables are preceded by
538 and immediately followed by the system variable name, which
551 <term>database</term>
554 Current database specified.
571 <term>Constant string</term>
574 A string used as part of the ID — surrounded
575 by single- or double quotes.
583 For instance, the sample GILS records that come with the Zebra
584 distribution contain a unique ID in the data tagged Control-Identifier.
585 The data is mapped to the Bib-1 use attribute Identifier-standard
586 (code 1007). To use this field as a record id, specify
587 <literal>(bib1,Identifier-standard)</literal> as the value of the
588 <literal>recordId</literal> in the configuration file.
589 If you have other record types that uses the same field for a
590 different purpose, you might add the record type
591 (or group or database name) to the record id of the gils
592 records as well, to prevent matches with other types of records.
593 In this case the recordId might be set like this:
596 gils.recordId: $type (bib1,Identifier-standard)
602 (see <xref linkend="data-model"/>
603 for details of how the mapping between elements of your records and
604 searchable attributes is established).
608 As for the file record ID case described in the previous section,
609 updating your system is simply a matter of running
610 <literal>zebraidx</literal>
611 with the <literal>update</literal> command. However, the update with general
612 keys is considerably slower than with file record IDs, since all files
613 visited must be (re)read to discover their IDs.
617 As you might expect, when using the general record IDs
618 method, you can only add or modify existing records with the
619 <literal>update</literal> command.
620 If you wish to delete records, you must use the,
621 <literal>delete</literal> command, with a directory as a parameter.
622 This will remove all records that match the files below that root
628 <sect1 id="register-location">
629 <title>Register Location</title>
632 Normally, the index files that form dictionaries, inverted
633 files, record info, etc., are stored in the directory where you run
634 <literal>zebraidx</literal>. If you wish to store these, possibly large,
635 files somewhere else, you must add the <literal>register</literal>
636 entry to the <literal>zebra.cfg</literal> file.
637 Furthermore, the Zebra system allows its file
638 structures to span multiple file systems, which is useful for
639 managing very large databases.
643 The value of the <literal>register</literal> setting is a sequence
644 of tokens. Each token takes the form:
647 <emphasis>dir</emphasis><literal>:</literal><emphasis>size</emphasis>.
650 The <emphasis>dir</emphasis> specifies a directory in which index files
651 will be stored and the <emphasis>size</emphasis> specifies the maximum
652 size of all files in that directory. The Zebra indexer system fills
653 each directory in the order specified and use the next specified
654 directories as needed.
655 The <emphasis>size</emphasis> is an integer followed by a qualifier
657 <literal>b</literal> for bytes,
658 <literal>k</literal> for kilobytes.
659 <literal>M</literal> for megabytes,
660 <literal>G</literal> for gigabytes.
664 For instance, if you have allocated two disks for your register, and
665 the first disk is mounted
666 on <literal>/d1</literal> and has 2GB of free space and the
667 second, mounted on <literal>/d2</literal> has 3.6 GB, you could
668 put this entry in your configuration file:
671 register: /d1:2G /d2:3600M
677 Note that Zebra does not verify that the amount of space specified is
678 actually available on the directory (file system) specified - it is
679 your responsibility to ensure that enough space is available, and that
680 other applications do not attempt to use the free space. In a large
681 production system, it is recommended that you allocate one or more
682 file system exclusively to the Zebra register files.
687 <sect1 id="shadow-registers">
688 <title>Safe Updating - Using Shadow Registers</title>
691 <title>Description</title>
694 The Zebra server supports <emphasis>updating</emphasis> of the index
695 structures. That is, you can add, modify, or remove records from
696 databases managed by Zebra without rebuilding the entire index.
697 Since this process involves modifying structured files with various
698 references between blocks of data in the files, the update process
699 is inherently sensitive to system crashes, or to process interruptions:
700 Anything but a successfully completed update process will leave the
701 register files in an unknown state, and you will essentially have no
702 recourse but to re-index everything, or to restore the register files
703 from a backup medium.
704 Further, while the update process is active, users cannot be
705 allowed to access the system, as the contents of the register files
706 may change unpredictably.
710 You can solve these problems by enabling the shadow register system in
712 During the updating procedure, <literal>zebraidx</literal> will temporarily
713 write changes to the involved files in a set of "shadow
714 files", without modifying the files that are accessed by the
715 active server processes. If the update procedure is interrupted by a
716 system crash or a signal, you simply repeat the procedure - the
717 register files have not been changed or damaged, and the partially
718 written shadow files are automatically deleted before the new updating
723 At the end of the updating procedure (or in a separate operation, if
724 you so desire), the system enters a "commit mode". First,
725 any active server processes are forced to access those blocks that
726 have been changed from the shadow files rather than from the main
727 register files; the unmodified blocks are still accessed at their
728 normal location (the shadow files are not a complete copy of the
729 register files - they only contain those parts that have actually been
730 modified). If the commit process is interrupted at any point during the
731 commit process, the server processes will continue to access the
732 shadow files until you can repeat the commit procedure and complete
733 the writing of data to the main register files. You can perform
734 multiple update operations to the registers before you commit the
735 changes to the system files, or you can execute the commit operation
736 at the end of each update operation. When the commit phase has
737 completed successfully, any running server processes are instructed to
738 switch their operations to the new, operational register, and the
739 temporary shadow files are deleted.
745 <title>How to Use Shadow Register Files</title>
748 The first step is to allocate space on your system for the shadow
750 You do this by adding a <literal>shadow</literal> entry to the
751 <literal>zebra.cfg</literal> file.
752 The syntax of the <literal>shadow</literal> entry is exactly the
753 same as for the <literal>register</literal> entry
754 (see <xref linkend="register-location"/>).
755 The location of the shadow area should be
756 <emphasis>different</emphasis> from the location of the main register
757 area (if you have specified one - remember that if you provide no
758 <literal>register</literal> setting, the default register area is the
759 working directory of the server and indexing processes).
763 The following excerpt from a <literal>zebra.cfg</literal> file shows
764 one example of a setup that configures both the main register
765 location and the shadow file area.
766 Note that two directories or partitions have been set aside
767 for the shadow file area. You can specify any number of directories
768 for each of the file areas, but remember that there should be no
769 overlaps between the directories used for the main registers and the
770 shadow files, respectively.
777 shadow: /scratch1:100M /scratch2:200M
783 When shadow files are enabled, an extra command is available at the
784 <literal>zebraidx</literal> command line.
785 In order to make changes to the system take effect for the
786 users, you'll have to submit a "commit" command after a
787 (sequence of) update operation(s).
793 $ zebraidx update /d1/records
800 Or you can execute multiple updates before committing the changes:
806 $ zebraidx -g books update /d1/records /d2/more-records
807 $ zebraidx -g fun update /d3/fun-records
814 If one of the update operations above had been interrupted, the commit
815 operation on the last line would fail: <literal>zebraidx</literal>
816 will not let you commit changes that would destroy the running register.
817 You'll have to rerun all of the update operations since your last
818 commit operation, before you can commit the new changes.
822 Similarly, if the commit operation fails, <literal>zebraidx</literal>
823 will not let you start a new update operation before you have
824 successfully repeated the commit operation.
825 The server processes will keep accessing the shadow files rather
826 than the (possibly damaged) blocks of the main register files
827 until the commit operation has successfully completed.
831 You should be aware that update operations may take slightly longer
832 when the shadow register system is enabled, since more file access
833 operations are involved. Further, while the disk space required for
834 the shadow register data is modest for a small update operation, you
835 may prefer to disable the system if you are adding a very large number
836 of records to an already very large database (we use the terms
837 <emphasis>large</emphasis> and <emphasis>modest</emphasis>
838 very loosely here, since every application will have a
839 different perception of size).
840 To update the system without the use of the the shadow files,
841 simply run <literal>zebraidx</literal> with the <literal>-n</literal>
842 option (note that you do not have to execute the
843 <emphasis>commit</emphasis> command of <literal>zebraidx</literal>
844 when you temporarily disable the use of the shadow registers in
846 Note also that, just as when the shadow registers are not enabled,
847 server processes will be barred from accessing the main register
848 while the update procedure takes place.
856 <!-- Keep this comment at the end of the file
861 sgml-minimize-attributes:nil
862 sgml-always-quote-attributes:t
865 sgml-parent-document: "zebra.xml"
866 sgml-local-catalogs: nil
867 sgml-namecase-general:t