Redo log Files

The redo log files are only used for recovery.
The redo log files oracle RDBMS  are only used for data recovery. The Oracle server maintains online redo log files to minimize the loss of data in the database. Thee redo log files  stores redo records written from the redo log buffer.

During a transaction, before a user receives a "Commit complete" message, the system must first successfully write the new or changed data to a redo log file.
All the changes during this transaction are first written into the log buffer. At the end of a transaction, the redo log buffer must be flushed to disk, else the recovery operations for that commit could not be guaranteed. It is LGWR (Log Writer) that does that flushing.

SQL> select blocksize from v$log;

SQL> select group#, sequence#, bytes, members, status
2 from v$log;


SQL> select group#, archived, status from v$log;

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