Writing redo records to the redo log files from the log buffer. Wait Time: Time it takes for the I/Os to complete. Even though redo records are written in parallel, the parallel write is not complete until the last I/O is on disk. Parameter Description files Number of files to be written blocks Number of…
Waiting for space in the log buffer because the session is writing data into the log buffer faster than LGWR can write it out. Consider making the log buffer bigger if it is small, or moving the log files to faster disks such as striped disks.
Used local archiving of online redo logs (for a production database) or standby redo logs (for a standby database). When the archiving process exhausts its I/O buffers because all of them are being used for on-going I/O’s, the wait for an available I/O buffer is captured in this system wait event.
When a user session commits, the session’s redo information needs to be flushed from memory to the redo logfile to make it permanent. At the time of commit, the user session will post the LGWR to write the log buffer (containing the current unwritten redo, including this session’s redo information) to the redo log file.…
Oracle Database Internal Mechanism 