Tales From A Lazy Fat DBA

Both ALTER SYSTEM SWITCH LOGFILE and ALTER SYSTEM ARCHIVELOG CURRENT will force a log switch, but they do it in different ways.

ARCHIVELOG CURRENT waits for the writing to complete.  This can take several minutes for multi-gigabyte redo logs.  Conversely, the ALTER SYSTEM SWITCH LOGFILE command is very fast and returns control to the caller in less than a second while ALTER SYSTEM ARCHIVELOG CURRENT pauses.

• ALTER SYSTEM  SWITCH LOGFILE is asynchronous:  This command is fast to return to the invoking program because the writing of the redo log to the OS filesystem is done in the background.  There is a very small risk in cases where the ARCH process cannot complete writing the redo log, such as cases where the OS archivelog file directory is out of space.  It is also risky because the calling script may move on to a subsequent step, assuming that the redo has been written.  Some scripts will place a SLEEP 60 command in their backup script to allow time for the redo to complete writing, but this is not a best practice.

• ALTER SYSTEM ARCHIVELOG CURRENT is synchronous:  This is faster to return because this command waits until the online redo log has completed the writing of the redo log file to the filesystem.  This command is safer because it waits for the OS to acknowledge (ACK) that the redo log has been successfully written.  Hence, ALTER SYSTEM ARCHIVELOG CURRENT is the best practice for production backup scripts with RMAN.

• ALTER SYSTEM ARCHIVE LOG ALL triggers an archive process if your DB (System) has archive logs that needs to be apply if still you try using the command you’ll receive below provided error message.

*
ERROR at line 1:
ORA-00271: there are no logs that need archiving