Performing backup and recovery of master and replica databases
To ensure that data is secure in the event of a system failure, always back up the master database and possibly also the replica databases on a periodic basis. Use the following guidelines:
▪ The normal disaster prevention and recovery tasks that you use on a non-synchronized solidDB database also apply to synchronized databases.
– You should automate backups to run during non-busy hours.
– For protection against disk crashes, after completing the backup, copy your backup files to tape or other media by using your backup software.
– You can make an online backup of any database of a solidDB system. Upon recovery, solidDB uses transaction log files to roll forward the backup database from the state of the backup to the state of the last committed transaction. The last persistent state of the synchronization is also restored at that time.
▪ Because the master database has the official version of data and the data in the replica databases are tentative, do not use a replica database as a backup for the master database. The last persistent state of a master database can be restored only from the backup files of the master database itself.
▪ If the master database is recovered from a backup without data loss (rollforward recovery is able to recover all the transactions from the log files), synchronization can proceed normally.
▪ If the master database is recovered with data loss, for example, due to missing transaction logs, the data loss is reflected in the replica databases during the next refresh. If synchronization data is not in sync between the master and replica databases, a full publication (all data in the publication) is sent to the replica database during the next refresh. This occurs regardless of whether the tables in the publication are set for incremental publication.
▪ A replica database can be reconstructed in the following ways:
– Restore the database from the backup of the replica database. Creating backups of the replica database is useful if the database is a large one and there is disk space available for the backup.
– Re-create the replica database and refresh the data from the master database.
Recreating (rather than restoring) the replica database is useful if the replica database is small and there is no local-only data in the replica database.
▪ When you restore any backup of a solidDB database, make sure that the restore is rolling forward all transactions to the latest committed transaction. This ensures that the synchronization continues from the point where it was when the database failed.
▪ After the restore is complete, verify that any possible ongoing synchronization messaging has been completed successfully in both the master and replica databases.