When the system operates online non-stop 24 hours per day, 365 days per year, you lose the time you need to perform database maintenance (tasks such as reorganizing databases, loading data, backing up, and so on). Moreover, creating a datamart for performing aggregate and analytical processing while online operations are ongoing might degrade network responses times when datamart operations such as extracting added or updated data are being performed. The inner replica facility remedies these kinds of situations.

Using a disk system or software that provides mirroring, the inner replica facility creates a replica database, which is a copy of the master database. Online operations use the replica database, while database maintenance and datamart creation operations use the master database. By employing the inner replica facility in this way, you can perform database maintenance and datamart creation operations concurrently with online operations.

The figure below provides an overview of the inner replica facility. For details about the inner replica facility, see the HiRDB Staticizer Option Version 9 Description and User's Guide.

Figure 2-1 Overview of the inner replica facility

The following subsections provide application examples of the inner replica facility.

(a) Reorganizing a database

You can use the inner replica facility to allow users to access and update a database while it is being reorganized. This is called updatable online reorganization. Unless you are using the inner replica facility, databases cannot be accessed or updated while they are being reorganized. In addition, the inner replica facility minimizes adverse affects on online operations, because normal work operations are performed with the replica database. The following figure shows reorganization of a database while the inner replica facility is being used.

Figure 2-2 Database reorganization while using the inner replica facility

Explanation

The database reorganization utility (pdrorg command) is used to reorganize the master database, while the replica database is used for online operations.

Before the database is reorganized, it is reflected and the current database is switched over. While this is occurring, the database cannot be accessed or updated. After the current database is switched over, the master database is reorganized, and the replica database is used for online operations. After reorganization is finished, the system logs from the replica database are used as input information to reflect to the master database, the updates that were performed during reorganization. This is called reflection processing.

(b) Making a backup

You can use the inner replica facility to allow users to access and update a database while it is being backed up. The following figure shows database backup while the inner replica facility is being used.

Figure 2-3 Making a backup while using the inner replica facility

Explanation

A backup is made from the replica database. The master database can still be accessed and updated while the backup is being made. If a failure occurs on the master database, the backup made from the replica database can be used to recover the master database.

(c) Creating a datamart

You can use the inner replica facility to create, from the replica database, a datamart to be used for analytical operations. This allows you to perform online operations and analytical operations at the same time. The following figure shows datamart creation while the inner replica facility is being used.

Figure 2-4 Datamart creation while using the inner replica facility

Explanation

A datamart for aggregate and analytical operations can be created from the replica database while online operations are ongoing. Analyzing data from a number of viewpoints increases the amount of data in the datamart, as well as the time required to create the datamart. By using the inner replica facility, you can create the datamart while online operations are being performed, without having to worry about the time it takes or the effects it has on online operations.