Planning the replication system

Answer these questions before you begin to install and configure the software.

Where is the primary data?

Determine which Adaptive Server databases contain the data you want to replicate to other databases.

NoteAlthough this document refers to Adaptive Server databases, the Heterogenous Datatype Support (HDS) translation feature allows you to select non-Adaptive Server databases for use with Replication Server. For more information, see “Installing and Implementing Heterogeneous Datatype Support”.

Where will you replicate the data?

Determine the Adaptive Server databases where Replication Server will maintain copies of the data.

What Replication Servers will you need?

When you design a replication system, you decide how many Replication Servers will be installed, which databases they will manage, and on which machine they will execute.

A Replication Server can manage one or more databases. One Replication Server is adequate for some replication systems. Other systems require a Replication Server at each geographic site to manage all of the databases at that site. Still others require multiple Replication Servers at each site to handle many databases or heavy transaction volumes.

When you upgrade Replication Servers, you can “phase in” the upgrades and install 15.0.1 Replication Servers initially only at certain sites. Consider the timing of such upgrades with care, and assess each site’s need for the new Replication Server features.

Where is the RSSD for each Replication Server?

Replication system data is stored in a dedicated Adaptive Server Enterprise database called the Replication Server System Database (RSSD), or embedded in an Adaptive Server Anywhere Database (ERSSD). RSSD must be actively managed, while ERSSD is automatically created, configured, and maintained by Replication Server. If you choose to use RSSD, it is created when the Replication Server is installed. Before you begin the installation, decide which Adaptive Server will store the RSSD for the Replication Server and the devices on which the database and its log will be stored. You can create the Adaptive Server database devices during installation, but identify their physical disk location before you install the Replication Servers. If you choose to use ERSSD, decide the directory paths for the ERSSD database file, transaction log, and backup. For better performance and recoverability, the database file, transaction log, and backup directory should be on different disk devices.

Where is the initial disk partition for each Replication Server?

Replication Server stores messages, such as replicated transactions, on disk in stable queues. Disk space for the queues is allocated from disk partitions you create. A disk partition can be a raw disk partition or an operating system file.

You must allocate a disk partition of at least 20MB for each Replication Server you install. You can add more partitions later if necessary. Check each partition to make sure that it is available and that the “sybase” user can write to it. To use an operating system file for a partition, create an empty file. Verify that there is enough space on the file system for Replication Server to extend the file to full partition size.

Which Replication Server is the ID Server?

The first Replication Server you install is the ID Server. It must be running when you install new Replication Servers or add databases to the replication system.

The ID Server assigns a unique site ID to each Replication Server and a unique database ID to each database in the replication system. It also maintains replication system version information.

Which databases require Replication Agents?

A Replication Agent retrieves transactions from a database log, and passes them to the replication system via the Replication Server that manages the database.

There is one Replication Agent per database. Because the Replication Agent is configured when a database is set up for replication, you must know whether a Replication Agent is required before you add a database to the replication system. A user database requires a Replication Agent if:

An RSSD requires a Replication Agent if the Replication Server using that RSSD has a route to another Replication Server; for example:

An RSSD does not require a RepAgent if the replication system has only one Replication Server. RepAgent for ERSSD is managed by Replication Server. It is automatically started when a route is created. You do not need to decide the ERSSD RepAgent requirements at installation or configuration time of Replication Server.

Which databases require warm standby?

Replication Server can maintain a warm standby database for an Adaptive Server database. If the active database fails, clients can switch to the standby database with little interruption.

To set up a warm standby application, you must perform some tasks in the Replication Server before and after you add databases to the replication system. Read Chapter 3, “Managing Warm Standby Applications” in the Replication Server Administration Guide Volume 2, before you install Replication Server.