Oracle Data Guard: Difference between revisions

Revision as of 17:18, 9 March 2009

Revision as of 21:54, 10 March 2009

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{{Howto}}

The software which [[Oracle Corporation]] markets as '''Oracle Data Guard''' forms an extension to the [[Oracle Database|Oracle]] [[database management system|RDBMS]]. It aids in establishing and maintaining secondary "[[standby database]]s" as alternative/supplementary repositories to production "primary databases".

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== Operation ==

A primary site which has an archived [[redo log]] to transfer invokes the '''RFSLNS''' (remote filelog-write network-server) and '''ARCH''' background process within the Oracle(archiver) instanceprocesses running on a standby host. The RFS process then performs the taskprimary ofdatabase receivingselect archived [[redo logslog]]s and sentsend fromthem to the primarystandby database. ,<ref>

{{cite web

| url = http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_DataGuardNetworkBestPractices.pdf

| title = Data Guard Redo Transport & Network Best Practices: Oracle Database 10g Release 2

| accessdate = 2009-03-11

| author =

| last = Smith

| first = Michael T

| authorlink =

| coauthors =

| date =

| year = 2007

| month = February

| format = PDF

| work =

| publisher = Oracle Corporation

| ___location =

| pages = 6, 14

| doi =

| archiveurl =

| archivedate =

| dateformat =

| quote = ... sending processes (LNS and ARC) on the production database....The Data Guard LNS process on the production database performs a network send to the Data Guard RFS process on the standby database.

}}

</ref>

where the '''RFS''' (remote file server) background process within the Oracle instance performs the task of receiving archived redo-logs originating from the primary database.

Alternatively, a supplementary mechanism may transfer the archived redo logs. On the standby database a '''Fetch Archive Log ('''FAL)''') client monitors for gaps in the sequence of received logs. If it finds a gap, it may invoke one or more Fetch Archive Log (FAL) servers to run on the primary database to forward the missing item(s).<ref>

[http://www.oracle-base.com/articles/9i/DataGuard.php Oracle-Base site summary of Data Guard], retrieved [[2007-09-05]]; [http://download.oracle.com/docs/cd/B28359_01/server.111/b28294/toc.htm Oracle Corp version 11.1 documentation links], retrieved [[2007-09-05]].

</ref>

Once the archived redo logs have arrived, other processes (such as an '''ARCH''' (Archiver process)''', an '''MRP''' (Managed Recovery Process)''', and/or an '''LSP''' (Logical Standby Process)''') may set about applying the log contents to the standby database.

== Advantages ==