Backup and Recovery Features
Oracle8i offers new backup and recovery
features. You can now archive to multiple archivelog destinations.
New features in Oracle standby databases make it much easier to
administer. Oracle8i introduced log miner, a tool that allows you to
mine the database redo logs for all sorts of information.
RMAN is just better in 8i. Most recovery catalog
requirements are gone. The duplicate command is new in 8i.
Tablespace point in time recovery is now supported and new views
help you monitor performance of RMAN (v$backup_sync_io and
Multiplexed Archived Redo Logs
Oracle8i now allows you to multiplex archived
redo log locations to up to 5 different locations. This is done with
the new log_archive_dest_n parameter. You can also define the
state of those locations with the log_archive_dest_state_n
parameter to enable or defer archiving to a defined location.
Standby database in Oracle8i now allows for
managed recovery mode. When the standby database is put in this
mode, it will apply redo from the primary database automatically
with no administrator interaction (or scripts) required. Note that
this mode is mutually exclusive with the standby database when it’s
open in read-only mode (another new feature!). To put the database
in managed recovery mode issue the following command:
recover managed standby database;
If you want to open your standby database in
read-only mode, issue the following command:
Alter database open read only;
When you are done, you can simply shutdown the
instance and then re-mount it to start managed recovery again.
Perhaps one of the most underutilized Oracle
utilities, logMiner was released in Oracle version 8i. This utility
reads the online and archived redo log file and populates views that
the Remote DBA can query to analyze the redo stream. With this utility you
can see most database changes, who made them and when. The
dbms_logmnr and dbms_logmnr_d packages are available in
8i to manage log miner operations and create the log miner
dictionary file. A new view, V$LOGMNR_CONTENTS is available to query
the results of your log mining session.
Oracl10g comes with a just a ton of
improvements (I like that word, plethora!) for RMAN. These include
The Flash Recovery Area
Using the catalog and uncatalog commands
Dropping a database in RMAN
Unregistering a database in RMAN
Making and Using RMAN backup copies
Configuring default disk backup types.
Changes to incremental backups.
Recovering datafiles not backed up.
Changes in error reporting.
Compressing RMAN Backups
RMAN Related TSPITR changes.
Oracle Database 10g Flashback Features
Oracle Database 10g offers a new set of
“Flashback” features that allow you to review database data, and
even reset the database, or database objects, to a point in time in
the past without actually having to perform a recovery.
Flashback query is a very powerful feature in
the Oracle database that was introduced in Oracle9i, and enhanced in
Oracle9i Release 2. Now, Oracle10g offers even more functionality in
the form of Flashback Database. Flashback database allows you to
flashback the entire database to a specific point in time.
Oracle10g offers flashback drop. This feature
allows you to undo the effects of a drop table command via
the new flashback table SQL command using the to before
Flashback Versions Query
Flashback versions query allows you to define
a minimum and maximum time (using the versions between timestamp
clause of the select statement) or scn range (using the
versions between SCN clause of the select statement), and
then query a specific row or set of rows in a table to see a list of
all values assigned to those rows.
Flashback Transaction Query
Oracle10g provides the ability to easily
reconstruct SQL statements that have been executed by SQL
statements. Previously, you would need to use Log Miner to generate
SQL redo statements that could be used to replicate SQL statements
executed in the database. Now, Flashback Transaction Query can be
used to reconstruct the SQL statements used to make changes in the
database, and those that can be used to undo the change.
The flashback table command allows you
to flashback an Oracle table based on timestamp or database SCN. All
flashback table operations must be at the beginning of any
transaction and flashback table operations are not supported for the