RE logical/physical standby database

1. Why logical standby database is SQL apply, and Physical standby database is redo apply? What ‘s the meaning/objective for that? (pls don’t tell me what is SQL/redo apply)
2. As we know, a logical standby database can be used for reporting and querying if primary database is down, why we still need a physical standby database (it can’t do that during recovering process, it just a same copy of primary database)? Why not just go ahead to set up only a perfect logical standby database? (just because logical one can’t accommodate all kinds of data type???)
3. Combined with Real time Apply and maximum protection, we can achieve a zero data loss, but could we achieve a zero downtime? Why or why not?

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>>>Can you convert a Logical standby to a Physical Standby?

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  • Logical standby database to physical standby database

    I already start my logical standby database and I want to return it again to physical standby database. So what should I do?

    >
    The "may be" is because I have tested flashback of a physical standby to before resetlogs, but not a logical standby.
    >
    A physical standby keeps the DBID of the primary - a logical standby does not. That is exactly the problem that restricts the reconversion into physical from logical, and you did not encounter that problem.
    >
    I haven't used "keep identity" but from what I read it relates to "convert to physical" not "flashback database".
    >
    Exactly. And that is what the OP wants to do: convert to physical (from logical).
    You mentioned that this might be possible with flashback.
    Problem: During the conversion from physical to logical, the DBID gets changed unless you specify (in 11g) KEEP IDENTITY. This would make it possible to reconvert into phyiscal from logical.
    In short: If there is no solution for the changed DBID of the logical standby in order to flashback it into physical as you suggested, then it is not possible .
    When I saw your first answer, I thought that you might have a solution in mind in order to solve that obvious problem. Sorry for having bothered you.
    Kind regards
    Uwe
    http://uhesse.wordpress.com

  • Physical Standby database Vs. Logical Standby database

    I have few questions regarding capability of Logical Standby Database against Physical Standby database.
    1. How efficient is Logical Standby database in terms of Physical Standby Database?? How both differ from each other and can I use Logical Standby Database for disaster Recovery?? Can It be use for recovering the failed Primary Instance?? If yes how efficient and reliable it is??
    2. What are the known bugs and roadblocks for logical standby database on Oracle 10.2.0.1 on Soalris X86-64?
    3.As logical standby database not going to replicate each and every schema of Primary database?? how is the change management effects to the logical standby from primary?? I mean there are some parameters and job that we create on primary how can it be transferred over to the logical standby??

    1. How efficient is Logical Standby database in terms
    of Physical Standby Database?? How both differ from
    each other and can I use Logical Standby Database for
    disaster Recovery?? Can It be use for recovering the
    failed Primary Instance?? If yes how efficient and
    reliable it is??I'm not sure what sort of "efficiency" you're talking about here...
    Physical standby is just the old, tried and true application of archived logs to recover a database. Very solid, very old school.
    Logical standby, on the other hand, is parsing the redo log, extracting logical change records, and applying them to the standby database. This obviously takes a bit more processing effort, it's newer technology, it doesn't have quite the level of support that physical standby does (i.e. certain data types are excluded), etc. You certainly can use it for failover, but it isn't quite as robust as a physical standby. Of course, this is getting better and better all the time and is definitely a focus of Oracle's development efforts.
    On the other hand, logical standby systems can do things other than act as a warm standby. They can be open serving reports, for example. You can create additional structures (i.e. new materialized views) to support reporting. A physical standby is pretty much always going to be in managed recovery mode, so it cannot be queried.
    2. What are the known bugs and roadblocks for logical
    standby database on Oracle 10.2.0.1 on Soalris
    X86-64?a) You'll want to do a Metalink search
    b) If you're talking about a high-availability solution, why are you looking at a base release of the database? Why wouldn't you apply the latest patchset?
    3.As logical standby database not going to replicate
    each and every schema of Primary database?? how is
    the change management effects to the logical standby
    from primary?? I mean there are some parameters and
    job that we create on primary how can it be
    transferred over to the logical standby??I'm not sure I understand... Changes made to the primary generate redo. Oracle parses that redo, generates a LCR, and sends that to the standby database where that change record gets applied.
    Justin

  • Will logical standby database be replaced by physical standby database?

    Will logical standby database be deprecated or replaced by physical standby database because of Real Time Query?
    As far as I know, because of the emergence of Real Time Query, physiacl standby database is easier to work than logical standby database. There are so many restrictions on using logical standby database.
    Will logical standby database be deprecated in the future?
    Message was edited by:
    frank.qian

    Good question - you are right that with the advent of Real Time Query, physical standby databases can provide the 'reporting database' functionality that you used to have to use a logical standby database for.
    But remember that logical standby databases allow additional schema objects, like materialized views and indexes, that you can't have with a physical standby (for the reasons Hans mentions). For example, you could have a index-light primary database for OLTP style workload, and an index-heavy logical standby, with MVs and dimensions for reporting, DW, etc.
    For this reason I don't expect logical standby will become deprecated.

  • Downtime for logical or physical standby database

    Hi ,
    Are there any downtime required to refresh the data from the primary database to logical standby or physical standby database. What are the pros and cons of
    using logical and physical standby database approach. which one is advisable to use in production environment.
    Regards,
    Richard

    Hi Richard,
    I'd suggest you read the documentation as a starting point, to answer your questions on here would be quite lengthy,
    http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/toc.htm
    In a nutshell you dont need downtime to maintain a standby, you can create them from a hot backup of your primary and get them recovering whilst it is open, in terms of which type of standby to use (physical or logical) that depends on your requirements for the use of the standby ... as I said read the doco (chapter 2 has a section on the benefits of each type).
    HTH
    Paul

  • Can i convert logical standby database to physical standby database

    Dear All,
    Can i convert a logical standby database to physical standby database?
    If yes, what are the steps to follow?
    Thanks
    Mahipal

    I never needed or tested something like this, but below maybe usefull -
    Transient Logical Standby
    Users can convert a physical standby to a transient logical standby database to effect a rolling database upgrade, and then revert the standby to its original state as a physical standby database once the upgrade is complete - using the KEEP IDENTITY clause. This benefits physical standby users who wish to execute a rolling database upgrade without investing in redundant storage otherwise needed to create a logical standby database.
    http://www.oracle.com/technology/deploy/availability/htdocs/DataGuardOverview.html
    But opposite is documented - http://download-west.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ls.htm#BEIGJCAC
    best regards.

  • How to convert logical standby database to Physical Standby Database

    Hi,
    Does anyone know how to convert logical standby database(10.2.0.3) to Physical Standby Database(10.2.0.3)? Is this possible? If so,please give me steps for it.
    Thanks.
    Regards,
    RJ.

    I don't believe this to be possible. One of the steps invloved in the creation of a logical standby is the following:
    ALTER DATABASE OPEN RESETLOGS;
    This makes the logical standby a different incarnation of the db from the primary.
    A physical standby is a binary copy of a primary db, a logical standby is a completely seperate db that just happens to get sql statements applied to it that are generated from a primary db, but is open read/write.
    One avenue, though would be if you had flashback database enabled and you flashed back all the way to when the db was a physical standby and then rolled forward with the archived redo logs.
    It's somewhat unlikely you are in that situation, but that is a possibility.
    Indeed the 11g snapshot standby does this sort of thing:
    http://download.oracle.com/docs/cd/B28359_01/server.111/b28294/manage_ps.htm#sthref740
    jason.
    http://jarneil.wordpress.com

  • Physical standby database to Logical standby

    Can I convert a physical standby database to Logical standby,

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    >>>Can you convert a Logical standby to a Physical Standby?

  • Issue on physical standby database

    Hi
    I've a problem on standby database.
    I recently added a datafile on primary database, then I scp'ed the data file to physical standby database.On physical standby database I tried performing recovery.
    I get following message in my alert log
    WARNING! Recovering data file 88 from a fuzzy file. If not the current file
    it might be an online backup taken without entering the begin backup command.
    ORA-279 signalled during: ALTER DATABASE RECOVER standby database ...
    how can I fix this now.
    We keep physical standby database 2 day behind, and apply logs manually.
    Physical standby database is maintained manually.
    Could someone help me in getting out of this problem.
    Oracle 9.2.0.7
    solaris

    Versus keeping it in manual mode, you can specify a time "delay" for the application of the logs:
    From http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/log_apply.htm#i1022811
    6.2.2 Specifying a Time Delay for the Application of Archived Redo Log Files
    In some cases, you may want to create a time lag between the time when redo data is received from the primary site and when it is applied to the standby database. You can specify a time interval (in minutes) to protect against the application of corrupted or erroneous data to the standby database. When you set a DELAY interval, it does not delay the transport of the redo data to the standby database. Instead, the time lag you specify begins when the redo data is completely archived at the standby destination.
    Note:
    If you define a delay for a destination that has real-time apply enabled, the delay is ignored.
    Specifying a Time Delay
    You can set a time delay on primary and standby databases using the DELAY=minutes attribute of the LOG_ARCHIVE_DEST_n initialization parameter to delay applying archived redo log files to the standby database. By default, there is no time delay. If you specify the DELAY attribute without specifying a value, then the default delay interval is 30 minutes.
    Canceling a Time Delay
    You can cancel a specified delay interval as follows:
    For physical standby databases, use the NODELAY keyword of the RECOVER MANAGED STANDBY DATABASE clause:
    SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY;
    For logical standby databases, specify the following SQL statement:
    SQL> ALTER DATABASE START LOGICAL STANDBY APPLY NODELAY;
    These commands result in log apply services immediately beginning to apply archived redo log files to the standby database, before the time interval expires. Also, see:
    Section 12.8, "Using a Physical Standby Database with a Time Lag"
    Oracle Database SQL Reference for the DELAY attribute of the ALTER DATABASE RECOVER MANAGED STANDBY DATABASE statement

  • How to open a "manual" Physical standby database in read/write mode

    Hi,
    I am running Oracle Database 10g Release 10.2.0.3.0 - 64bit Production Standard Edition on Linux version 2.6.9-42.0.8.ELsmp ([email protected]) (gcc version 3.4.6 20060404 (Red Hat 3.4.6-3))
    I've created a physical standby database, but since I am running Standard Edition, I am not using the DataGuard features. I use the rsync utility to copy over the archivelogs to the standby database, and I apply them periodically to the standby database.
    The standby database is started this way :
    startup nomount pfile='/u01/oradata/orcl/initorcl.stdby';
    alter database mount standby database;
    Everything runs perfectly fine, I can do "alter database open read only" and then I can do selects into tables to confirm that everything is up to date.
    The thing is, if I shutdown immediate the database, then do just startup :
    shutdown immediate;
    startup;
    The database opens with no error messages, but is still in read-only mode...
    I read that the default behavior for a standby database is to open read-only, like I am experiencing, but I would like to know what is the right way to open it correctly in read-write mode (I understand that after that, my standby will not be standby anymore and that I will have to recreate my standby database).
    Thanks,
    Mat

    Hello,
    There're features which allows you to open a Standby database in Read/Write mode but for all I know
    it needs Entreprise Edition.
    In Enterprise Edition you can use Logical Standby database. More over, for Physical standby there's
    a way by using flashback database so as to rolling backward the database and avoiding to recreate
    the Standby.
    In Standard Edition I'm afraid that you'll have to recreate your Standby database.
    Best regards,
    Jean-Valentin

  • More than One Physical Standby Database

    Hi All!
    Is it possible to have more than one physical standby database? Does the procedure on how to create a single physical standby is the same as creating more than one? How about the configuration of the Primary database? Im planning this because I want the other physical standby to be used for read only access for our testing environment.
    Please enlighten me.
    Regards,
    cmadiam

    Think about it.
    Q. What's the crux of Dataguard setup?
    A. Redo transfer from primary to standby
    Q.Which is the parameter you use to direct the redo transfer
    A. LOG_ARCHIVE_DEST_n
    Q. How many LOG_ARCHIVE_DEST_n parameters can be set?
    A. 10; LOG_ARCHIVE_DEST_1 to LOG_ARCHIVE_DEST_10
    Of the 10 LOG_ARCHIVE_DEST_n, one of them should be LOCAL destination, which means you can have 9 other REMOTE destinations ~~ 9 standby database. Physical or logical or mix of both.
    Cheers.
    Note: Each of the 9 standby database can cascade redo transfer to 9 other cascaded standby databases. WOW! now you do the math.

  • Physical Standby Database with slight complication

    Hello Database experts,
    Primary is a multi-node RAC instance , primarily two distinct schemas (for simplicity sake schema A on tablespace A1/A2 and schema B on tablespace B1/B2). There is a proposed physical standby database. Now primary is Enterprise Data warehouse with millions of updates per minute. Is it possible to somehow bypass objects owned by schema A to be propogated on DR instance.
    Any workaround possible?
    Assume that Hot backup of primary database backup has to be done so we can not perform nologging operations on schema A and Logical standby is not a option.
    Kind Regards,
    Sunil

    ***Is it possible to somehow bypass objects owned by schema A to be propogated on DR instance.***
    Yes. but not in physical standby. While bypassing the objects to physical standby the recovery cannot be enabled at the time. So data loss may occur. Try to configure logical standby database. you can get what you expect.
    thanks

  • Cannot Clear Critical Alert for Physical Standby Databases

    10.2.0.4.0 Grid Control monitoring 10.2.0.4.0 databases and standby databases with 10.2.0.4.0 agents.
    The standby databases are running on Xen guests. The O/S is Red Hat 4 Advanced Server.
    I had a failure of Xen guest on Saturday that caused me to have to rebuild the standby servers. EM Grid Control successfully verifies the configurations and the status is normal for both physical standby databases. (A rebuilt logical standby database shows no alerts.)
    Grid Control database targets page shows a single critical alert for each physical standby database. The alert is for "number of missing media files is 4". The metric graph shows the count as 0 since before the rebuilds. I cannot clear the alerts from the Critical Alerts page. Grid Control reports "The selected alert(s) cannot be manually cleared. They will clear automatically once the metric is no longer in a critical or warning state.".
    Any suggestions?
    Thanks,
    Ray Westphal

    Thanks for the reply Anthony.
    The result of the query on both standby databases is '0'. The metric graph also shows the value at '0' since before rebuilds.
    And the OMS db and agents have been reset several times since I posted this.
    Ray Westphal.

  • Clarification on creating a Physical Standby Database

    I'm practicing with data guard with Oracle 10.2.0.1.0 on two Windows 2003 servers.
    I'm in the process of creating a physical standby database by following the steps outlined in the guide http://www.filibeto.org/sun/lib/nonsun/oracle/10.2.0.1.0/B19306_01/server.102/b14239/create_ps.htm
    I've created the primary database and did a cold backup of all the datafiles and copied them to the standby server using OS commands. I've created a pfile from the spile in primary database and changed the needed parameters for the standby database.
    What I don't understand is this statement I think is creating a control file for the standby database: SQL> ALTER DATABASE CREATE STANDBY CONTROLFILE AS '/tamp/standby.ctl'
    Exactly what I don't understand is what to do with this control file. I'm thinking that if I try to use it as the controlfile for the standby database, the standby database will refuse to open since the database name in the control file wont match the one the server expects.
    I don't want to proceed until this becomes clear. So my question is what to do with the output of the above statement that seems to create a control file for the standby database.
    Any help would be appreciated.
    Dula

    >
    You're thinking wrong.
    Please clarify the difference between db_name and
    db_unique_name.
    Db_unique_name needs to be identical for both primary
    AND standby database.
    If db_unique_name differs, you'll get errors.
    Sybrand,
    Perhaps, you meant DB_NAME has to be identical for both databases.
    DB_NAME name has to be the same for both primary and physical standby database.
    DB_UNIQUE_NAME should be unique for each database in the standby configuration.
    http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#i68626
    If you configure Logical Standby Database, DB_NAME may be different.
    For the original poster: Chapter 3 - Creating a Physical Standby Database of Oracle® Data Guard Concepts and Administration has all the steps you have to do in order to configure a physical standby database.
    http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm#g88234
    Cheers,

  • Bringing a Physical Standby database online without (a) tablespace(s)

    Dear all,
    Is it possible to create a kind of "dblink" in a physical standby database residing in a remote host (another host than the primary production database)? We want to make this standby DB to be online without one tablespace.
    Our database consists of 2 parts: a core part (around 55 Gb) - stored in 2 tablespaces, residing in one mounted disk - and an "attachment" part (around 550 Gb) - stored in one tablespace, residing in 2 mounted disks. The attachment part is of less importance. We would like to make a standby DB for the core part and exclude the attachment part (because of its extensive size) to be online.
    Currently we can not put this physical standby DB online, since it requires the attachment datafiles to be available.
    Would it be a problem if we NFS mount these 2 disks on the host where the standby database resides?
    The best solution would be if we can tell the standby DB that there is no need to update the attachment tablespace.
    Thanx a lot for anyone reading, thinking and most of all give the solution for my problem...
    Agape
    Thanx in advance.

    Hi Sybrand,
    Since we only will use the standby DB in read only mode, maybe the use of a Logical one will be usefull afterall.
    Can you please explain how to configure this need (having a standby DB without this one large TB) in a Logical standby DB?
    Your help will be highly appreciated.
    Thanx
    Solution found: Bringing physical standby database to online

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