163 lines
9.4 KiB
HTML
163 lines
9.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Commands used for working with DataLinks" />
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<meta name="abstract" content="Support for the DataLink data type can be broken down into three different components." />
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<meta name="description" content="Support for the DataLink data type can be broken down into three different components." />
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<meta name="DC.subject" content="data types, DataLinks, commands used" />
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<meta name="keywords" content="data types, DataLinks, commands used" />
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<meta name="DC.Relation" scheme="URI" content="rbafydatalinks.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Identifier" content="rbafydlcommands" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Commands used for working with DataLinks</title>
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</head>
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<body id="rbafydlcommands"><a name="rbafydlcommands"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Commands used for working with DataLinks</h1>
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<div><p>Support for the DataLink data type can be broken down into three
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different components.</p>
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<div class="section"> <ol><li>The DB2<sup>®</sup> database
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support has a data type called DATALINK. This can be specified
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on SQL statements such as CREATE TABLE and ALTER TABLE. The column cannot
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have any default other than NULL. Access to the data must be using SQL interfaces.
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This is because the DataLink itself is not compatible with any host variable
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type. SQL scalar functions can be used to retrieve the DataLink value in
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character form. There is a DLVALUE scalar function that must be used in SQL
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to INSERT and UPDATE the values in the column.</li>
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<li>The DataLink File Manager (DLFM) is the component that maintains the link
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status for the files on a server, and keeps track of meta-data for each file.
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This code handles linking, unlinking, and commitment control issues. An
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important aspect of DataLinks is that the DLFM need not be on the same physical
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system as the SQL table that contains the DataLink column. So an SQL table
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can link an object that resides in either the same system's integrated file
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system, or a remote server's integrated file system.</li>
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<li>The DataLink filter must be run when the file system tries operations
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against files that are in directories designated as containing linked objects.
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This component determines if the file is linked, and optionally, if the user
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is authorized to access the file. If the file name includes an access token,
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the token will be verified. Since there is extra overhead in this filter
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process, it is only run when the accessed object exists in one of the directories
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within a DataLink prefix. See the discussion below on prefixes.</li>
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</ol>
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</div>
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<div class="section"><p>When working with DataLinks, there are several steps that must
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be taken to properly configure the system: </p>
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<ul><li>TCP/IP must be configured on any systems that are going to be used when
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working with DataLinks. This includes the systems on which the SQL tables
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with DataLink columns are going to be created, as well as the systems that
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will contain the objects to be linked. In most cases, this will be the same
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system. Since the URL that is used to reference the object contains a TCP/IP
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server name, this name must be recognized by the system that is going to contain
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the DataLink. The command CFGTCP can be used to configure the TCP/IP names,
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or to register a TCP/IP name server. </li>
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<li>The system that contains the SQL tables must have the Relational Database
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Directory updated to reflect the local database system, and any optional remote
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systems. The command WRKRDBDIRE can be used to add or modify information
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in this directory. For consistency, it is recommended that the same names
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be used as the TCP/IP server name and the Relational Database name. </li>
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<li>The DLFM server must be started on any systems that will contain objects
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to be linked. The command STRTCPSVR *DLFM can be used to start the DLFM server.
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The DLFM server can be ended by using the CL command ENDTCPSVR *DLFM.</li>
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</ul>
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</div>
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<div class="section"><p>Once the DLFM has been started, there are some steps needed to
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configure the DLFM. These DLFM functions are available via an executable
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script that can be entered from the QShell interface. To get to the interactive
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shell interface, use the CL command QSH. This will open a command entry screen
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from which you can enter the DLFM script commands. The script command dfmadmin
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-help can be used to display help text and syntax diagrams. For the most
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commonly used functions, CL commands have also been provided. Using the CL
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commands, most or all of the DLFM configuration can be accomplished without
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using the script interface. Depending on your preferences, you can choose
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to use either the script commands from the QSH command entry screen or the
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CL commands from the CL command entry screen. </p>
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</div>
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<div class="section"><p>Since these functions are meant for a system administrator or
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a database administrator, they all require the *IOSYSCFG special authority. </p>
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</div>
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<div class="section"></div>
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<div class="section"><h4 class="sectiontitle">Add a prefix</h4><p>A prefix is a path or directory that
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will contain objects to be linked. When setting up the Data Links File Manager
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(DLFM) on a system, the administrator must add any prefixes that will be used
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for DataLinks. The script command dfmadmin -add_prefix is used to add prefixes.
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The CL command to add prefixes is Add Prefix to DataLink File Manager (ADDPFXDLFM)
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command.</p>
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<p>For instance, on server TESTSYS1, there is a directory called
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/mydir/datalinks/ that contains the objects that will be linked. The administrator
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uses the command ADDPFXDLFM PREFIX(('/mydir/datalinks/')) to add the prefix.
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The following links for URLs are valid since their path beings with a valid
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prefix:</p>
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</div>
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<div class="example"> <pre>http://TESTSYS1/mydir/datalinks/videos/file1.mpg
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or
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file://TESTSYS1/mydir/datalinks/text/story1.txt </pre>
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</div>
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<div class="section"><p>It is also possible to remove a prefix using the script command
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dfmadmin -del_prefix. This is not a commonly used function since it can only
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be run if there are no linked objects anywhere in the directory structure
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contained within the prefix name.</p>
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</div>
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<div class="section"> <div class="note"><span class="notetitle">Notes:</span> <ol><li>The following directories, or any of their subdirectories, should not
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be used as prefixes for DataLinks: <ul><li>/QIBM</li>
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<li>/QReclaim</li>
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<li>/QSR</li>
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<li> /QFPNWSSTG</li>
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</ul>
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</li>
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<li>Additionally, common base directories such as the following should not
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be used unless the prefix is a subdirectory within one of the base directories: <ul><li>/home</li>
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<li>/dev</li>
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<li>/bin</li>
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<li>/etc</li>
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<li>/tmp</li>
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<li>/usr</li>
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<li>/lib</li>
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</ul>
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</li>
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</ol>
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</div>
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</div>
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<div class="section"><h4 class="sectiontitle">Add a host database</h4><p>A host database is a relational
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database system from which a link request originates. If the DLFM is on the
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same system as the SQL tables that will contain the DataLinks, then only the
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local database name needs to be added. If the DLFM will have link requests
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coming from remote systems, then all of their names must be registered with
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the DLFM. The script command to add a host database is dfmadmin -add_db and
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the CL command is Add Host Database to DataLink File Manager (ADDHDBDLFM)
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command. This function also requires that the libraries containing the SQL
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tables also be registered.</p>
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<div class="p">For instance, on server TESTSYS1, where you
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have already added the /mydir/datalinks/ prefix, you want SQL tables on the
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local system in either library TESTDB or PRODDB to be allowed to link objects
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on this server. Use the following command: <pre>ADDHDBDLFM HOSTDBLIB((TESTDB) (PRODDB)) HOSTDB(TESTSYS1)</pre>
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</div>
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</div>
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<div class="section"><p>Once the DLFM has been started, and the prefixes and host database
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names have been registered, you can begin linking objects in the file system. </p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafydatalinks.htm" title="The DataLink data type is one of the basic building blocks for extending the types of data that can be stored in database files. The idea of a DataLink is that the actual data stored in the column is only a pointer to the object.">Use DataLinks</a></div>
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</div>
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</div>
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</body>
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</html>
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