The term materialization refers to the process of copying the contents of one database (the source) to another (the target), so that both databases contain identical data. This is the prerequisite condition (or starting point) for any system that provides continuous data replication, including the Mirror Activator system.
Materialization always replaces existing data (if any) in the target database with the data in the source database. Therefore, any process that copies only the differences between the source data and the target data (for example, an “incremental replication”) is not materialization.
Some materialization techniques copy all of the source data to the target, but for only part of the source database (for example, subscription materialization in Replication Server). Such techniques are not well suited for databases in the Mirror Activator system.
The Mirror Activator system is intended to replicate a complete database, with a one-to-one relationship between each object in one primary database and each object in one standby database. Because the Mirror Activator system relies on mirror log devices, which are exact copies of the primary database log devices, a device-level database materialization technique may be well suited for a Mirror Activator system.
Snapshot materialization allows you to take advantage of your disk replication system’s facilities to simplify the materialization process, and to reduce the time required for a complete database materialization.
Choosing the materialization technique to use will depend on several factors:
Using your disk replication solution will typically provide the fastest transfer mechanism, but it may require skills that the typical DBA is not familiar with.
Hardware system administrators may be comfortable with disk replication configuration and file system organization but less familiar with timing and commands required for database execution and reloading.
Existing copy mechanisms used by your organization may provide slower raw transfer rates but faster overall execution time, simply due to having existing familiarity with the technique.
Therefore, the choice of materialization technique is left to individual discretion.
The Mirror Activator system setup procedures in Chapter 2, “Setting Up and Configuring Mirror Activator,” and the failover and failback procedures in Appendix B, “Failover and Failback with Mirror Activator,” are based on using the snapshot materialization technique.
Snapshot materialization requires the primary database
to be quiesced. To minimize primary database downtime, refer to
the appropriate task checklist in the following sections and plan
your materialization procedures carefully. For more information,
refer to the Mirror Replication Agent Primary Database Guide.
