Progress Fathom Replication
User’s Guide

> ## Transition configuration

> For transitioning to operate properly, it must be configured. The following section defines automatic and manual transition processing and the use of one or two target databases.

> ##### Choosing one or two target databases

> Fathom Replication allows for up to two target databases, though only one of the target databases can be used to automatically transition into a normal Progress database. The target database that will automatically transition to a normal Progress database in a failure condition is the first target database whose `[control-agent.agent]` properties in the `server.repl.properties` file has `critical` set to `1` and `transition` set to `auto`. If you set more than one target database to `crtitical=1` and`transition=auto`, Fathom Replication will only recognize the first target database specified in the `server.repl.properties` file for automatic transition. The second database will have to be transitioned manually.

> The target database you choose as critical is the database you can use as a hot standby should the source database become unavailable. This target database should be on a machine that has reliable TCP/IP connectivity and has the resources for clients to connect to and perform database updates should your source database become unavailable.

> Only one target database should be designated to transition. If you transition two target databases and users make updates to both databases, you will not have a single target database with which to resource your source database.

> ##### Automatic transition

> When the Fathom Replication agent loses contact with the Fathom Replication server, it will wait for a configured amount of time, known as `transition-timeout`, for the server to reconnect. If the Fathom Replication server does not reconnect before the `transition-timeout` expires, the target database will be transitioned to a normal database by the agent.

> For automatic transition to be performed by the Fathom Replication agent, the following must be true:

> - The Fathom Replication server property, `transition`, must be set to `auto`.

> - The control-agent property, `critical`, must be set to `1`.

> - The server property, `transition-timeout`, must be set to a reasonable value.

> The sample property file in Figure 2–3 can be used as a guide.

>     # Fathom Replication properties file for a database that will be used
>     # as both a source and target database for Fathom Replication.
>     #
>     [server]
>         control-agents=agent1
>         database=source
>         transition=auto
>         transition-timeout=1200
>     [control-agent.agent1]
>         name=agent1
>         database=target
>         host=localhost
>         port=4502
>         connect-timeout=120
>         replication-method=async
>         critical=1

> Figure 2–3: Server properties file with auto transition

> As Figure 2–3 shows, the Fathom Replication agent,`agent1`, waits for connection from the Fathom Replication server for 1200 seconds, or 20 minutes, before it performs transition.

> ##### Manual transition

> With manual transition, when the Fathom Replication agent loses contact with the Fathom Replication server, it waits indefinitely for a transition to be performed by the DBA. If the Fathom Replication server reconnects any time before transition is performed, normal processing resumes. In order for manual transition to be performed by the Fathom Replication agent, the following must be configured:

> - The server property, `transition`, must be set to `manual`.

> - The control-agent property, `critical`, can be set to `1` or `0`.

> - The server property, `transition-timeout`, should be set to a reasonable value. Even though this value is not used for manual transition, it should be set in case transition is changed to `auto`.

> The sample property file in Figure 2–4 can be used as a guide.

>     # Fathom Replication properties file for a database that will be used
>     # as both a source and target database for Fathom Replication.
>     #
>     [server]
>         control-agents=agent1
>         database=source
>         transition=manual
>         transition-timeout=1200
>     [control-agent.agent1]
>         name=agent1
>         database=target
>         host=localhost
>         port=4502
>         connect-timeout=120
>         replication-method=async
>         critical=0

> Figure 2–4: Server properties file with manual transition

> As Figure 2–4 shows, the Fathom Replication agent, agent1, will wait for connection from the Fathom Replication server indefinitely for the DBA to perform transition.

> To perform transition manually, use the following command:

>     DSRUTIL target_db_name -C transition Agent

> Note: Before performing a manual transition, see the "Manually applying After Image extents" section.

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