Backup and Recovery on the Host

This section contains an outline of the recommended methods for backing up and recovering a Reality database from the host and Reality environments.

Introduction

Saving and restoring a Reality database for back-up and recovery purposes can be carried out from Reality or from the host environment:

Two methods are suggested.

• Use Reality Save facilities to back-up databases to one or more tape images, and then use host back-up utilities to back-up the rest of the host file system (including the tape images).

  An advantage of this method is that a database can be saved while database users are still logged on. This may be necessary if 24 hour a day user access to the database is required, in which case it is recommended that the save is carried out when user activity is at a minimum.

• Use a host back-up utility to back-up the entire host system, including databases.

  With this method, all Reality database users must normallySome backup utilities (for example, those supplied by VERITAS) allow users to continue working, because they use a checkpointing method to ignore changes to a database that occur after the backup has started. The realdump host utility allows you to temporarily freeze database operation so that checkpointing can be initiated. be logged off before the utility is run. The database should be locked to prevent more users logging on. Ideally, the whole host file system should be quiescent before a host back-up or restore is carried out:

  • On UNIX systems, this can be ensured by setting the system into single-user mode. If you carry out a UNIX backup in multi-user mode, it is recommended that you perform the back-up when system activity is at a minimum. It may be useful to send a message requesting a pause in activities or even asking users to log off or stop working on file systems until the back-up is complete.

  • On Windows, the whole file system should ideally be quiescent before a Windows back-up or restore is carried out, because the standard Windows backup utility will not backup any files that are open during the backup. When backing up Reality files using the Windows backup utility, it is recommended that you first use realserv -e to stop the Reality service.