Program modules

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Redo logs: Redo logs are special files in the Oracle database, which ensure that all changes made by the session will be recorded in the logs in case there is a failure between the moment the changes are made and the moment they are written to the data files. Thus, repeat execution logs are the basis of the recovery process.

Oracle organizes its repeat execution log files into log groups, and you need to have at least two different groups of repeat execution logs and at least one member in each. At the very least, two groups will be required, because when one re-execution log is archived, the log writer process should be able to continue writing to the active re-execution log.

Although the Oracle database will work well enough with only one member in each group of repeat execution logs, Oracle strongly recommends multiplexing online repeat execution logs.…