Archive Log Files
Archive log files are actually the saved redo
log files. When a redo log file is filled up and
the next redo log file is put to use, the filled
redo log file is saved or archived. The saved
files are known as archive log files.
Automatic archiving can be enabled on the redo
log. Oracle automatically archives redo log
files when the database in is in ARCHIVELOG
mode.
The archive logs are written to the
destination specified by the
log_archive_dest
parameter and the optional
log_archive_duplex_dest
parameter.
If sending the archived log files to a
remote destination is required, then the
log_archive_dest_n
parameter
would be used where n is an integer from 1 to
10.
The
log_archive_dest_n parameter
supports both local and remote destinations.
The
log_archive_dest and
log_archive_duplex_dest only
support local destinations.
In RAC, a separate set of archive log files is
created by each instance. Since each RAC
instance has its own redo log files, the
corresponding archive log files are produced
when the log switch takes place. The archive log
files may be written to a local file system or
to a cluster file system. Oracle does not insist
upon a particular type of file system. Writing
to a clustered file system has the added
advantage of being available to archive all the
nodes in the cluster, which becomes important in
case of media recovery.
Parameter File (SPFILE)
The attributes of an instance depend on the
initialization parameters used for starting up
the instance. Initialization parameters control
the configuration of the database system. They
are the key directives to start and manage any
instance. While launching the database instance,
parameters are specified, and they remain until
the instance is shutdown. Optionally, certain
parameters may be modified during the instance
run time by the ALTER SYSTEM SET method,
provided the instance has been started with the
SPFILE method.
The SPFILE feature allows the changing of
parameter values dynamically. It also allows
them to be set either permanently or in memory
only. For Oracle Real Application Clusters
(RAC), one server parameter file can be used and
shared among instances. The usage of a single
copy of the SPFILE for the entire database
provides administrative convenience and
simplification. The SPFILE must be located on a
clustered file system.
Password File
The password file is another important file that
is shared by all the instances of Oracle 11g
RAC. This file, which is stored in binary
format, records all of the authentication
privileges granted to the users.
Privileges such as SYSDBA or SYSOPER are
recorded in this file.
The password file is required for remote
authentication for the users with SYSDBA or
SYSOPER privileges. This file is located on the
shared file system.
Alert Log File and Trace Files
In Oracle 11g, alert and trace files are stored
in the Automatic Diagnostic Repository
(ADR).
ADR is a fault diagnosability
infrastructure for preventing, detecting,
diagnosing, and resolving problems.
The problem categories are database code
bugs, metadata corruption, and user data
corruption.
Oracle 11g maintains two alert log files:
a text formatted and XML formatted file.
The alert log file, background trace
files, and server process trace files are
created in the ADR.
The new 11g
diagnostic_dest
parameter determines the ADR location.
Each instance in the RAC database writes to the
alert log file and produces trace files
periodically. The alert log file contains all of
the messages generated by the Oracle database
kernel. Trace files contain detailed information
about a specific event or issue. These log and
trace files help the administrators keep track
of the database activity and assist in
troubleshooting.
Upon instance startup, the database
writes all non-default parameter settings to the
alert log file.
The alter log file and trace files may be
written either to a directory within a local
file system or within the cluster file system.
NOTE: Rampant author Laurent Schneider has some
additional insight into
creating an Oracle Automatic Diagnostic
Repository (ADR).
