Write-Ahead Logging (WAL) in PostgreSQL and Redo Logs in Oracle are both designed to maintain data integrity an safe data merging. Oracle uses the pre-configured logs (Redo.logs)and will emit warnings or error messages when a log cannot be reused. PostgreSQL on the other hand  adds more WAL files to a directory named "pg_xlog",if   existing log can't be reused . This prevents PostgreSQL database from stalling if a transaction was not completed as directed. In Oracle it may freeze the db when an a log can't be archived or flushed.
Redo log Files : In PostgreSQL system creates WAL segment files, which are allocated with 16MB storage size for each WAL segment files, and system renames the  segment files which are non-longer-needed with higher segment numbers . The  files of WAL or redo log 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. The 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;