Alter Log For Free

Answer: As you noted, the "alter system switch logfile" command forces a log switch. It will produce an archived redo log that is smaller than the size dictated by the size of the log_buffer parameter, which governs the size of the redo log RAM buffer.

Oracle has two ways to force a logfile switch. ALTER SYSTEM SWITCH LOGFILE; ALTER SYSTEM ARCHIVE LOG CURRENT; Both will force a log switch log and move to another available redo log file(having status inactive).

Argument required: The ALTER SYSTEM ARCHIVE LOG CURRENT allows you to specify the thread to archive while the ALTER SYSTEM SWITCH LOGFILE archives only the current thread. If you do not pass the thread parameter, Oracle will archive all full online redo logs.

RAC: If you are running RAC, the ALTER SYSTEM ARCHIVE LOG CURRENTwill switch the logs on all RAC nodes (instances), whereas ALTER 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.

The Oracle Alert Log can be found inside the database Automatic Diagnostics Repository (ADR), which is a hierarchical file-based repository for diagnostic information: $ADR_BASE/diag/rdbms/{DB-name}/{SID}/trace .

The SQL statement ALTER SYSTEM CHECKPOINT explicitly forces Oracle to perform a checkpoint for either the current instance or all instances. Forcing a checkpoint ensures that all changes to the database buffers are written to the datafiles on disk. The GLOBAL option of ALTER SYSTEM CHECKPOINT is the default.

A log switch occurs when LGWR stops writing to one redo log group and starts writing to another. By default, a log switch occurs automatically when the current redo log file group fills. You can force a log switch to make the currently active group inactive and available for redo log maintenance operations.

The SWITCH LOGFILE clause lets you explicitly force Oracle Database to begin writing to a new redo log file group, regardless of whether the files in the current redo log file group are full.

Because most log files are recorded in plain text, the use of any text editor will do just fine to open it. By default, Windows will use Notepad to open a LOG file when you double-click on it. You almost certainly have an app already built-in or installed on your system for opening LOG files.

To view alert log, first you need to find it's location using show parameter command. To view alert log you can use tail command with options and filename. In the following output you will see the last 20 lines of the alert log, but if you want to see more number of lines (ex: 100 line) you can use 100f like that.