REDOLOG VS ARCHIVE LOG

SQL> SELECT distinct member LOGFILENAME FROM V$LOGFILE;

LOGFILENAME
--------------------------------------------------------------------------------
/u01/install/APPS/data/ebsdb/log1.dbf
/u01/install/APPS/data/ebsdb/log2.dbf
/u01/install/APPS/data/ebsdb/log3.dbf

ALTER SYSTEM SWITCH LOGFILE vs
ALTER SYSTEM ARCHIVE LOG CURRENT

hat is the difference between ALTER SYSTEM SWITCH LOGFILE and ALTER SYSTEM ARCHIVE LOG CURRENT, and when do I use each?
Answer:  Yes, both ALTER SYSTEM SWITCH LOGFILE and ALTER SYSTEM ARCHIVE LOG CURRENT will force a log switch, but they do it in different ways! 
Both the SWITCH LOGFILE and ARCHIVE LOG CURRENT write a quiesce checkpoint, a firm place whereby that last redo log is a part of the hot backup, but ARCHIVE LOG 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 ARCHIVE LOG CURRENT pauses.
As we see below, the ALTER SYSTEM SWITCH LOGFILE is fast because it does not wait for the archiver process (ARCH) to complete writing the online redo log to the archivelog log filesystem:

1. It issues database checkpoint
2.  It immediately starts writing to the next redo log
3.  In the background, the "switch logfile" command tells the ARCH background process to copy the "old" redo log file to the redo log filesystem.  

Here are the important differences between ALTER SYSTEM SWITCH LOGFILE and ALTER SYSTEM ARCHIVE LOG CURRENT:

•  RAC:  If you are running RAC, the ALTER SYSTEM ARCHIVE LOG CURRENTwill switch the logs on all RAC nodes (instances), whereasALTER SYSTEM SWITCH LOGFILE will only switch he logfile on the instance where you issue the switch command.  Hence, ALTER SYSTEM ARCHIVE LOG CURRENT is a best practice for RAC systems.

ENABLING ARCHIVELOG and SWITCHING LOG

SQL> archive log list

Database log mode              No Archive Mode

Automatic archival             Disabled

Archive destination            /u01/install/APPS/data/ebsdb/archive

Oldest online log sequence     7

Current log sequence           9

SQL> shut immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount;

ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance

ORACLE instance started.

Total System Global Area 2147483648 bytes

Fixed Size                  2926472 bytes

Variable Size             553650296 bytes

Database Buffers         1577058304 bytes

Redo Buffers               13848576 bytes

Database mounted.

SQL> alter database archivelog;

Database altered.

SQL> alter database open;

Database altered.

SQL> archive log list;

Database log mode              Archive Mode

Automatic archival             Enabled

Archive destination            /u01/install/APPS/data/ebsdb/archive

Oldest online log sequence     7

Next log sequence to archive   9

Current log sequence           9

SQL> alter switch logfile;

alter switch logfile

      *

ERROR at line 1:

ORA-00940: invalid ALTER command

SQL> ALTER SYSTEM SWITCH LOGFILE ;

System altered.

SQL> archive log list;

Database log mode              Archive Mode

Automatic archival             Enabled

Archive destination            /u01/install/APPS/data/ebsdb/archive

Oldest online log sequence     8

Next log sequence to archive   10

Current log sequence           10

SQL> exit