RE: Data Guard question

From: Sweetser, Joe <>
Date: Mon, 13 Oct 2008 08:56:08 -0600
Message-ID: <E323160E08E560459CD05A883546C3CE0D5C2E18@Earthquake.ICAT.COM>

In a nutshell, I think the answer is yes. Note they are NOT a requirement for all DG configurations, though.


From the DG Concepts & Administration manual:

2.5.2 Standby Redo Logs

A standby redo log is similar to an online redo log, except that a standby redo log is used to store redo data received from another database.

A standby redo log is required if you want to implement:

  • The maximum protection and maximum availability levels of data protection (described in Section 1.4 and in more detail in Section 5.6)
  • Real-time apply (described in Section 6.2)
  • Cascaded destinations (described in Appendix E)

A standby redo log provides a number of advantages:

  • Standby redo log files can reside on raw devices, which may be important if either or both the primary and standby databases reside in a Real Application Clusters environment.
  • Standby redo log files can be multiplexed using multiple members, improving reliability over archived log files.
  • During a failover, Data Guard can recover and apply more redo data from standby redo log files than from the archived log files alone.
  • The archiver (ARCn) process or the log writer (LGWR) process on the primary database can transmit redo data directly to remote standby redo log files, potentially eliminating the need to register a partial archived log file (for example, to recover after a standby database crashes). See Chapter 5 for more information.

-----Original Message-----
Sent: Monday, October 13, 2008 8:42 AM
To: Sweetser, Joe
Subject: RE: Data Guard question

Why does that requirement for an additional srl exist? Is it so that the target system can always keep up


-----<> wrote: -----

To: Bradd Piontek <>, <>, <>
From: "Sweetser, Joe" <> Sent by: <>
Date: 13/10/2008 03:21PM
cc: oracle-l <>
Subject: RE: Data Guard question

Not unexpectedly, it ended up be a combination of a few things:

  1. Not enough standby redo logs - recommended value is one more than the number of redo logs

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Received on Mon Oct 13 2008 - 09:56:08 CDT

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