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diff --git a/docs/programmer_reference/rep_replicate.html b/docs/programmer_reference/rep_replicate.html index 4068e278..dd848b85 100644 --- a/docs/programmer_reference/rep_replicate.html +++ b/docs/programmer_reference/rep_replicate.html @@ -3,28 +3,27 @@ <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> - <title>Running Replication using the db_replicate Utility</title> + <title>Running replication using the db_replicate utility</title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" /> <link rel="up" href="rep.html" title="Chapter 12. Berkeley DB Replication" /> <link rel="prev" href="rep_mgrmulti.html" title="Running Replication Manager in multiple processes" /> - <link rel="next" href="rep_mgr_ack.html" title="Choosing a Replication Manager Ack Policy" /> + <link rel="next" href="rep_mgr_ack.html" title="Choosing a Replication Manager acknowledgement policy" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> - <p>Library Version 11.2.5.3</p> + <p>Library Version 12.1.6.1</p> </div> <table width="100%" summary="Navigation header"> <tr> - <th colspan="3" align="center">Running Replication using the db_replicate Utility</th> + <th colspan="3" align="center">Running replication using the + db_replicate utility</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="rep_mgrmulti.html">Prev</a> </td> - <th width="60%" align="center">Chapter 12. - Berkeley DB Replication - </th> + <th width="60%" align="center">Chapter 12. Berkeley DB Replication </th> <td width="20%" align="right"> <a accesskey="n" href="rep_mgr_ack.html">Next</a></td> </tr> </table> @@ -34,7 +33,8 @@ <div class="titlepage"> <div> <div> - <h2 class="title" style="clear: both"><a id="rep_replicate"></a>Running Replication using the db_replicate Utility</h2> + <h2 class="title" style="clear: both"><a id="rep_replicate"></a>Running replication using the + db_replicate utility</h2> </div> </div> </div> @@ -42,125 +42,159 @@ <dl> <dt> <span class="sect2"> - <a href="rep_replicate.html#idp2251336">One Replication Process and Multiple Subordinate Processes</a> + <a href="rep_replicate.html#idp1926936">One replication process and multiple subordinate processes</a> </span> </dt> <dt> <span class="sect2"> - <a href="rep_replicate.html#idp2268704">Common Use Case</a> + <a href="rep_replicate.html#idp1906152">Common use case</a> </span> </dt> <dt> <span class="sect2"> - <a href="rep_replicate.html#idp2278848">Avoiding Rollback</a> + <a href="rep_replicate.html#idp1939624">Avoiding rollback</a> </span> </dt> <dt> <span class="sect2"> - <a href="rep_replicate.html#idp2283896">When to Consider an Integrated HA Application</a> + <a href="rep_replicate.html#idp1937856">When to consider an integrated replication application</a> </span> </dt> </dl> </div> - <p>Replication Manager supports shared access to a database -environment from multiple processes. Berkeley DB provides a -replication-aware utility, db_replicate, that enables you to upgrade an existing Transactional Data Store -application, as discussed in the <a class="xref" href="transapp.html#transapp_intro" title="Transactional Data Store introduction">Transactional Data Store introduction</a> section, -to an HA application with -minor modifications. While the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility simplifies the use -of replication with a TDS application, you -must still understand replication and its impact on the application. -</p> + <p> + Replication Manager supports shared access to a database + environment from multiple processes. Berkeley DB provides a + replication-aware utility, db_replicate, that enables you to + upgrade an existing Transactional Data Store application, as + discussed in the <a class="xref" href="transapp.html#transapp_intro" title="Transactional Data Store introduction">Transactional Data Store introduction</a> section, to a replication + application with minor modifications. While the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility + simplifies the use of replication with a Transactional Data + Store application, you must still understand replication and + its impact on the application. + </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> - <h3 class="title"><a id="idp2251336"></a>One Replication Process and Multiple Subordinate Processes</h3> + <h3 class="title"><a id="idp1926936"></a>One replication process and multiple subordinate processes</h3> </div> </div> </div> - <p>Based on the terminology introduced in the <a class="xref" href="rep_mgrmulti.html" title="Running Replication Manager in multiple processes">Running Replication Manager in multiple processes</a> section, -application processes are "subordinate processes" and the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility -is the "primary replication process".</p> <p> -You must consider the following items when -planning to use the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility in combination with -a TDS application. -</p> + Based on the terminology introduced in the <a class="xref" href="rep_mgrmulti.html" title="Running Replication Manager in multiple processes">Running Replication Manager in + multiple processes</a> + section, application processes are subordinate processes + and the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility is the replication process. + </p> + <p> + You must consider the following items when planning to + use the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility in combination with a Transactional + Data Store application. + </p> <div class="itemizedlist"> <ul type="disc"> - <li>Memory regions - <p> - The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility requires shared memory access among - separate processes, and therefore cannot be used with <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a>. - </p></li> - <li>Multi-process implications - <p> - You must understand and accept all of the TDS implications - of multi-process use as specified in <a class="xref" href="transapp_app.html" title="Architecting Transactional Data Store applications">Architecting Transactional Data Store applications</a>. Special attention should be - paid to the coordination needed for unrelated processes to - start up correctly. - </p></li> - <li>Replication configuration - <p> - Several configuration settings are required for replication. - You must set the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_REP" class="olink">DB_INIT_REP</a> - and <a href="../api_reference/C/dbopen.html#open_DB_THREAD" class="olink">DB_THREAD</a> flags for the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> method. - Another required configuration item is the local address. You identify - this by creating a <a href="../api_reference/C/db_site.html" class="olink">DB_SITE</a> handle and then setting the - <code class="literal">DB_LOCAL_SITE</code> parameter using the - <a href="../api_reference/C/dbsite_set_config.html" class="olink">DB_SITE->set_config()</a> method. You also tell sites how to contact other - sites by creating <a href="../api_reference/C/db_site.html" class="olink">DB_SITE</a> handles for those sites. - Most replication configuration options start with reasonable - defaults, but applications have to customize - at least some of them. You can set all replication related configuration options - either programmatically or in the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file. - </p></li> - <li> Starting the application and replication - <p> - The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility assumes that an - environment exists and that the application has run recovery, - if necessary, and created and configured the environment. - The startup flow of a typical TDS application may not be the - best flow for a replication application and you - must understand the issues involved. - For instance, if an application starts, runs recovery, - and performs update operations before starting the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility, - then if that site becomes a client when replication starts, - those update operations will be rolled back. - </p></li> - <li> Handling events - <p> - Almost all of the replication-specific events are handled - by the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process, and therefore the application - process does not see them. If the application needs to know - the information from those replication-specific events, such as - role changes, the application must call the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method method. - The one replication-specific event the application can now - receive is the <a href="../api_reference/C/envevent_notify.html#event_notify_DB_EVENT_REP_PERM_FAILED" class="olink">DB_EVENT_REP_PERM_FAILED</a> event. - See <a class="xref" href="rep_mgr_ack.html" title="Choosing a Replication Manager Ack Policy">Choosing a Replication Manager Ack Policy</a> - for additional information about this event. - </p></li> - <li> Handling errors - <p> - There are some error return values that relate only to replication. - Specifically, the <code class="literal">DB_REP_HANDLE_DEAD</code> error should now be handled - by the application. Also, if master leases are in use, then the - application also needs to consider the <code class="literal">DB_REP_LEASE_EXPIRED</code> error. - </p></li> - <li> Flexibility tradeoff - <p> - You are giving up flexibility - for the ease of use of the utility. - Application complexity or requirements may eventually - dictate integrating HA calls into the application - over using the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. </p></li> - <li> Read-only client application - <p> - The application requires additional changes to manage - the read-only status when the application takes on the role of - a client. - </p></li> + <li> + Memory regions + <p> + The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility + requires shared memory access among separate + processes, and therefore cannot be used with + <a href="../api_reference/C/envopen.html#envopen_DB_PRIVATE" class="olink">DB_PRIVATE</a>. + </p></li> + <li> + Multi-process implications + <p> + You must + understand and accept all of the Transactional + Data Store implications of multi-process use as + specified in <a class="xref" href="transapp_app.html" title="Architecting Transactional Data Store applications">Architecting Transactional Data + Store applications</a>. Special + attention should be paid to the coordination + needed for unrelated processes to start up + correctly. + </p></li> + <li> + Replication configuration + <p> + Several + configuration settings are required for + replication. You must set the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_REP" class="olink">DB_INIT_REP</a> and + <a href="../api_reference/C/dbopen.html#open_DB_THREAD" class="olink">DB_THREAD</a> flags for the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> method. + Another required configuration item is the local + address. You identify this by creating a <a href="../api_reference/C/db_site.html" class="olink">DB_SITE</a> + handle and then setting the + <code class="literal">DB_LOCAL_SITE</code> parameter + using the <a href="../api_reference/C/dbsite_set_config.html" class="olink">DB_SITE->set_config()</a> method. You also + tell sites how to contact other sites by creating + <a href="../api_reference/C/db_site.html" class="olink">DB_SITE</a> handles for those sites. Most replication + configuration options start with reasonable + defaults, but applications have to customize at + least some of them. You can set all replication + related configuration options either + programmatically or in the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file. + </p></li> + <li> + Starting the application and replication + <p> + The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility assumes that an environment + exists and that the application has run recovery, + if necessary, and created and configured the + environment. The startup flow of a typical + Transactional Data Store application may not be + the best flow for a replication application and + you must understand the issues involved. For + instance, if an application starts, runs recovery, + and performs update operations before starting the + <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility, then if that site becomes a client + when replication starts, those update operations + will be rolled back. + </p></li> + <li> + Handling events + <p> + Almost all of the + replication-specific events are handled by the + <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process, and therefore the + application process does not see them. If the + application needs to know the information from + those replication-specific events, such as role + changes, the application must call the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method + method. The one replication-specific event the + application can now receive is the + <a href="../api_reference/C/envevent_notify.html#event_notify_DB_EVENT_REP_PERM_FAILED" class="olink">DB_EVENT_REP_PERM_FAILED</a> event. See <a class="xref" href="rep_mgr_ack.html" title="Choosing a Replication Manager acknowledgement policy">Choosing a Replication Manager acknowledgement policy</a> for additional + information about this event. + </p></li> + <li> + Handling errors + <p> + There are some error + return values that relate only to replication. + Specifically, the + <code class="literal">DB_REP_HANDLE_DEAD</code> error + should now be handled by the application. Also, if + master leases are in use, then the application + also needs to consider the + <code class="literal">DB_REP_LEASE_EXPIRED</code> error. + </p></li> + <li> + Flexibility tradeoff + <p> + You are giving up + flexibility for the ease of use of the utility. + Application complexity or requirements may + eventually dictate integrating replication calls + into the application instead of using the + <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. + </p></li> + <li> + Read-only client application + <p> + The + application requires additional changes to manage + the read-only status when the application takes on + the role of a client. + </p></li> </ul> </div> </div> @@ -168,197 +202,218 @@ a TDS application. <div class="titlepage"> <div> <div> - <h3 class="title"><a id="idp2268704"></a>Common Use Case</h3> + <h3 class="title"><a id="idp1906152"></a>Common use case</h3> </div> </div> </div> <p> -This section lists the steps needed to get replication running for -a common use case of the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. -The use case presented is an existing TDS application that -already has its environment and databases created and is up and running. -At some point, HA is considered because failover protection -or balancing the read load may now be desired. -</p> + This section lists the steps needed to get replication + running for a common use case of the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. The + use case presented is an existing Transactional Data Store + application that already has its environment and databases + created and is up and running. At some point, replication + is considered because failover protection or balancing the + read load may now be desired. + </p> <div class="orderedlist"> <ol type="1"> <li> - <p> - To understand the issues involved in a replication/HA application, see - the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility section in the <span class="emphasis"><em>API Reference Guide</em></span>, the <a href="../api_reference/C/rep.html" class="olink">Replication Chapter</a> in the <span class="emphasis"><em> - Programmer's Reference Guide</em></span>, and the source code of the ex_rep_mgr - example program. - </p> + <p> + To understand the issues involved in a + replication application, see the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility + section in the <span class="emphasis"><em>API Reference + Guide</em></span>, the <a href="../api_reference/C/rep.html" class="olink">Replication Chapter</a> in the + <span class="emphasis"><em> Programmer's Reference + Guide</em></span>, and the source code of the + ex_rep_mgr example program. + </p> </li> <li> - <p> - Make a local hot backup of the current - application environment to a new location to use as a testing area. - </p> + <p> + Make a local hot backup of the current + application environment to a new location to use + as a testing area. + </p> </li> <li> - <p> - Add the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_REP" class="olink">DB_INIT_REP</a> and <a href="../api_reference/C/dbopen.html#open_DB_THREAD" class="olink">DB_THREAD</a> flags (if not already - being used) to the application or the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file. - </p> + <p> + Add the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_REP" class="olink">DB_INIT_REP</a> and <a href="../api_reference/C/dbopen.html#open_DB_THREAD" class="olink">DB_THREAD</a> flags (if + not already being used) to the application or the + <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file. + </p> </li> <li> <p> - Modify the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file to add the necessary replication - configuration values. At a minimum, the local - host and port information must be added using - the <a href="../api_reference/C/repmgr_site_parameter.html" class="olink">repmgr_site</a> method parameter. - As more sites are added to the group, remote host and port - information can optionally also be added by adding - more <a href="../api_reference/C/repmgr_site_parameter.html" class="olink">repmgr_site</a> method parameters to the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file file. - </p> + Modify the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file to add the necessary + replication configuration values. At a minimum, + the local host and port information must be added + using the <a href="../api_reference/C/repmgr_site_parameter.html" class="olink">repmgr_site</a> method parameter. As + more sites are added to the group, remote host and + port information can optionally also be added by + adding more <a href="../api_reference/C/repmgr_site_parameter.html" class="olink">repmgr_site</a> method parameters to + the <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file. + </p> </li> <li> - <p> - Rebuild the application and restart - it in the current testing directory. - </p> + <p> + Rebuild the application and restart it in the + current testing directory. + </p> </li> <li> <p> - Start the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility on the master site with the -M option and - any other options needed such as -h for the home directory. - At this point you have a lone master site running in an - environment with no other replicated sites in the group. - </p> + Start the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility on the master site + with the -M option and any other options needed + such as -h for the home directory. At this point + you have a lone master site running in an + environment with no other replicated sites in the + group. + </p> </li> <li> - <p> - Optionally, prepare to start a client site by performing a - manual hot backup of the running master environment to - initialize a client target directory. While replication - can make its own copy, the hot backup will expedite the - synchronization process. Also, if the application assumes - the existence of a database and the client site is started - without data, the application may have errors or incorrectly - attempt to create the database. - </p> + <p> + Optionally, prepare to start a client site by + performing a manual hot backup of the running + master environment to initialize a client target + directory. While replication can make its own + copy, the hot backup will expedite the + synchronization process. Also, if the application + assumes the existence of a database and the client + site is started without data, the application may + have errors or incorrectly attempt to create the + database. + </p> </li> <li> <p> - Copy the application to the client target. - </p> + Copy the application to the client target. + </p> </li> <li> - <p> - Modify the client environment's <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file to set the client's local host and port values and to add - remote site information for the master site and any - other replication configuration choices necessary. - </p> + <p> + Modify the client environment's <a href="../api_reference/C/configuration_reference.html" class="olink">DB_CONFIG</a> file to + set the client's local host and port values and to + add remote site information for the master site + and any other replication configuration choices + necessary. + </p> </li> <li> - <p> - Start the application on the client. The client application - should not update data at this point, as explained previously. - </p> + <p> + Start the application on the client. The client + application should not update data at this point, + as explained previously. + </p> </li> <li> - <p> - Start the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility specifying the - client environment's home directory using the -h option. Omit the -M - option in this case, because the utility defaults to - starting in the client role. - </p> + <p> + Start the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility specifying the client + environment's home directory using the -h option. + Omit the -M option in this case, because the + utility defaults to starting in the client role. + </p> </li> </ol> </div> - <p> -Once the initial replication group is established, do not use the -M option with -the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. -After the initial start, <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility assumes the use of -elections. If a site crashes, it should rejoin the group as -a client so that it can synchronize with the rest of the group. -</p> + <p> + Once the initial replication group is established, do + not use the -M option with the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility. After the + initial start, the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility assumes the use of + elections. If a site crashes, it should rejoin the group + as a client so that it can synchronize with the rest of + the group. + </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> - <h3 class="title"><a id="idp2278848"></a>Avoiding Rollback</h3> + <h3 class="title"><a id="idp1939624"></a>Avoiding rollback</h3> </div> </div> </div> + <p> + Depending on how an application is structured, + transactional rollback can occur. If this is possible, + then you must make application changes or be prepared for + successful transactions to disappear. Consider a common + program flow where the application first creates and opens + the environment with recovery. Then, immediately after + that, the application opens up the databases it expects to + use. Often an application will use the <a href="../api_reference/C/dbopen.html#open_DB_CREATE" class="olink">DB_CREATE</a> flag so + that if the database does not exist it is created, + otherwise the existing one is used automatically. Then the + application begins servicing transactions to write and + read data. + </p> <p> -Depending on how an application is structured, transactional rollback -can occur. If this is possible, then you must make application -changes or be prepared for successful transactions to disappear. -Consider a common program flow where the application first creates -and opens the environment with recovery. Then, immediately after -that, the application opens up the databases it expects to use. -Often an application will use the <a href="../api_reference/C/dbopen.html#open_DB_CREATE" class="olink">DB_CREATE</a> flag so that if the -database does not exist it is created, otherwise the existing one is -used automatically. Then the application begins servicing transactions -to write and read data. -</p> + When replication is introduced, particularly via the + <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility, the possibility of rollback exists unless + the application takes steps to prevent it. In the + situation described above, if all of the above steps occur + before the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process starts, and the site is + started as a client, then all the operations will be + rolled back when the site finds the master. The client + site will synchronize with the log and operations on the + master site, so any operations that occurred in the client + application before it knew it was a client will be + discarded. + </p> <p> -When replication is introduced, particularly via the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility, the -possibility of rollback exists unless the application takes steps -to prevent it. In the situation described above, if all of the -above steps occur before the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process starts, and -the site is started as a client, then all the operations will be -rolled back when the site finds the master. The client site will -synchronize with the log and operations on the master site, so -any operations that occurred in the client application before it -knew it was a client will be discarded. -</p> - <p> -One way to reduce the possibility of rollback is to modify the -application so that it only performs update operations (including -creation of a database) if it is the master site. If the application -refrains from updating until it is the master, then it will not perform -operations when it is in the undefined state before replication -has been started. -The event indicating a site is master will be delivered to the -<a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process, so the application process must look -for that information via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method. -A site that is expecting to perform updates may need to poll -via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method to see the state change from an undefined -role to either the master or client role. Similarly, since a -client site cannot create a database, it may need to poll for -the database's existence while the client synchronizes with the master -until the database is created at the client site. -</p> + One way to reduce the possibility of rollback is to + modify the application so that it only performs update + operations (including creation of a database) if it is the + master site. If the application refrains from updating + until it is the master, then it will not perform + operations when it is in the undefined state before + replication has been started. The event indicating a site + is master will be delivered to the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility process, + so the application process must look for that information + via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method. A site that is expecting to perform + updates may need to poll via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method to see the + state change from an undefined role to either the master + or client role. Similarly, since a client site cannot + create a database, it may need to poll for the database's + existence while the client synchronizes with the master + until the database is created at the client site. + </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> - <h3 class="title"><a id="idp2283896"></a>When to Consider an Integrated HA Application</h3> + <h3 class="title"><a id="idp1937856"></a>When to consider an integrated replication application</h3> </div> </div> </div> + <p> + The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility provides the means to achieve a + replicated application quickly. However, the trade-off for + this rapid implementation is that the full flexibility of + replication is not available. Some applications may + eventually need to consider integrating directly with + replication rather than using the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility if + greater flexibility is desired. + </p> <p> -The <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility provides the means to achieve -a replicated application quickly. However, -the trade-off for this rapid implementation is that the full -flexibility of replication is not available. Some applications -may eventually need to consider integrating directly with -replication rather than using the <a href="../api_reference/C/db_replicate.html" class="olink">db_replicate</a> utility if greater flexibility is desired. -</p> - <p> -One likely reason for considering integration would be the -convenience of receiving all replication-related events in -the application process and gaining direct knowledge of such -things as role changes. -Using the event callback is cleaner and easier than -polling for state changes via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method. -</p> + One likely reason for considering integration would be + the convenience of receiving all replication-related + events in the application process and gaining direct + knowledge of such things as role changes. Using the event + callback is cleaner and easier than polling for state + changes via the <a href="../api_reference/C/repstat.html" class="olink">rep_stat()</a> method. + </p> <p> -A second likely reason for integrating replication directly -into the application is the multi-process aspect of the -utility program. The developer may find it easier to insert -the start of replication directly into the code once the -environment is created, recovered, or opened, and avoid -the scenario where the application is running in the -undefined state. Also it may simply be easier to start -the application once than to coordinate different processes -and their startup order in the system. -</p> + A second likely reason for integrating replication + directly into the application is the multi-process aspect + of the utility program. The developer may find it easier + to insert the start of replication directly into the code + once the environment is created, recovered, or opened, and + avoid the scenario where the application is running in the + undefined state. Also it may simply be easier to start the + application once than to coordinate different processes + and their startup order in the system. + </p> </div> </div> <div class="navfooter"> @@ -372,11 +427,12 @@ and their startup order in the system. <td width="40%" align="right"> <a accesskey="n" href="rep_mgr_ack.html">Next</a></td> </tr> <tr> - <td width="40%" align="left" valign="top">Running Replication Manager in multiple processes </td> + <td width="40%" align="left" valign="top">Running Replication Manager in + multiple processes </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> - <td width="40%" align="right" valign="top"> Choosing a Replication Manager Ack Policy</td> + <td width="40%" align="right" valign="top"> Choosing a Replication Manager acknowledgement policy</td> </tr> </table> </div> |