Tales from Demo Grounds part 1: Clone PDBs while open READ-WRITE

DISCLAIMER: I’ve got this information by chatting with Oracle developers at the Demo Grounds. The functionality is not documented yet and Oracle may change it at its sole discretion.¬†Please refer to the documentation if/when it will be updated ūüėČ

In one of¬†my previous posts named “A PDB is cloned while in read-write, Data Guard loose its marbles (12.1.0.2, ORA-19729)” I’ve blogged about a weird behaviour:

The documentation states that you can create a pluggable database from another one only if the source PDB is open read-only.

Indeed, If I try to clone it when the source PDB is MOUNTED, I get error ORA-65036:

The weird behavior is that if you do it when the source is in read-write mode, it works from release 12.1.0.2 (onward?)

I’ve questioned the developers at the DEMO Grounds and they have confirmed that:

  • With the 12.1.0.2, they have initially planned to disclose¬†this functionality (clone PDBS in READ-WRITE).
  • That they had problems in making it work with an Active Data Guard environment (a-ah! so my post was not completely wrong)
  • Finally they have released it as undocumented feature
  • In the next release “they will fix it, maybe” and document it
  • The process of cloning the PDB anyway freeze the transactions on the source

I hope that this update helps clarifying both the behavior and my previous post about this problem! ūüôā

Cheers

Ludo

Oracle RAC, Oracle Data Guard, and Pluggable Databases: When MAA Meets Oracle Multitenant (OOW14)

Here you can find the material related to my session at Oracle Open World 2014. I’m sorry I’m late in publishing them, but I challenge you to find spare time during Oracle Open World! It’s the busiest week of the year! (Hard Work, Hard Play)

 Slides

 Demo 1 video

Demo 2 video

Demo 1 script

 

Demo 2 script

 

There’s one slide describing the procedure for cloning one PDB using the standbys clause. Oracle has released a Note while I was preparing my slides (one month ago) and I wasn’t aware of it, so you may also checkout this note on MOS:

Making Use of the STANDBYS=NONE Feature with Oracle Multitenant (Doc ID 1916648.1)

UPDATE: I’ve blogged about it in a more recent post: Tales from the Demo Grounds part 2: cloning a PDB with ASM and Data Guard (no ADG)

UPDATE 2:¬†I’ve written another blog post about these topics: Cloning a PDB with ASM and Data Guard (no ADG) without network transfer

Cheers!

 

Ludovico

Oracle Active Data Guard 12c: Far Sync Instance, Real-Time Cascade Standby, and Other Goodies

Here you can find the content related to my second presentation at Oracle Open World 2014.

 Slides

Demo video1: Real-Time Cascade

Demo video2: Far Sync Instance

Demo 1 Script

 

Demo 2 script

For the demo I’ve used 5 machines running 3 database instances and 2 Far Sync instances. I cannot provide the documentation for creating the demo environment, but the scripts may be useful to understand how the demo works.

Cheers

Ludo

A PDB is cloned while in read-write, Data Guard loose its marbles (12.1.0.2, ORA-19729)

UPDATE: please check my more recent post about this problem and the information I’ve got at the Oracle Demo Grounds during OOW14: http://www.ludovicocaldara.net/dba/demo-grounds-clone-pdb-rw/

I feel the strong need to blog abut this very recent problem because I’ve spent a lot of time debugging it… especially because there’s no information about this error on the MOS.

Introduction
For a lab, I have prepared two RAC Container databases in physical stand-by.
Real-time query is configured (real-time apply, standby in read-only mode).

Following the doc, http://docs.oracle.com/database/121/SQLRF/statements_6010.htm#CCHDFDDG, I’ve cloned one local pluggable database to a new PDB and, because Active Data Guard is active, I was expecting the PDB to be created on the standby and its files copied without problems.

BUT! I’ve forgot to put my source PDB in read-only mode on the primary and, strangely:

  • The pluggable database has been created on the primary WITHOUT PROBLEMS (despite the documentation explicitly states that it needs to be read-only)
  • The recovery process on the standby stopped with error.

 

Now, the primary had all its datafiles (the new PDB has con_id 4):

 

and the standby was missing the datafiles of the new PDB:

 

But, on the standby database, the PDB somehow was existing.

 

I’ve tried to play a little, and finally decided to disable the recovery for the PDB (new in 12.1.0.2).
But to disable the recovery I was needing to connect to the PDB, but the PDB was somehow “inexistent”:

 

So I’ve tried to drop it, but off course, the standby was read-only and I could not drop the PDB:

 

Then I’ve shutted down the standby, but one instance hung and I’ve needed to do a shutdown abort (I don’t know if it was related with my original problem..)

 

After mounting again the standby, the PDB was also accessible:

 

So I’ve been able to disable the recovery:

 

Then, on the primary, I’ve took a fresh backup of the involved datafiles:

 

and I’ve copied and cataloged the copies to the controlfile:

 

but the restore was impossible, because the controlfile was not knowing these datafiles!!

 

So I’ve RESTARTED the recovery for a few seconds, and because the PDB had the recovery disabled, the recovery process has added the datafiles and set them offline.

 

Then I’ve been able to restore the datafiles ūüôā

 

Finally, I’ve enabled again the recovery for the PDB and restarted the apply process.

 

Lesson learned: if you want to clone a PDB never, ever, forget to put your source PDB in read-only mode or you’ll have to deal with it!! ūüôā

Dataguard check script for Real Application Clusters (MAA)

Two years after my posts:
Quick Oracle Dataguard check script and More about Dataguard and how to check it I faced a whole new Dataguard between two Oracle Real Application Clusters, aka Oracle Maximum Availability Architecture (MAA).

This enviromnent is relying on Windows OS. Don’t know how this could be called “availability” but here we are. I revisited my scripts in a quick and very dirty way. Please consider that I did copy and paste to check the alignment once per thread, but it should be improved with some kind of iteration to check each thread in a more structured fashion.

Please foreward me every improvement you implement over my code: it would be nice to post it here.

More about Dataguard and how to check it

After my post Quick Oracle Dataguard check script I have some considerations to add:
to check the gap of applied log stream by MRP0 process it’s sufficient to replace this query in the perl script I posted:

with this new one:

To check this you have to meet the following condition: You should have real-time apply enabled (and possibly NODELAY clause specified in your recover statement). Check it with this query:

It should be “MANAGED REAL TIME APPLY”.
If not using realtime apply your MRP0 process will wait until you have a new archive, so even if you have redo transport mode set to LGWR you’ll wait for standby log completion. Your gap of applied redo stream will be at least one sequence#.

With transport mode set to LGWR and real-time apply the output of the perl script is similar to this one:

The whole gap between your primary and standby database should be LOW.

Quick Oracle Dataguard check script

Oracle Dataguard has his own command-line dgmgrl to check the whole dataguard configuration status.
At least you should check that the show configuration command returns SUCCESS.

This is an hypothetic script:

Another script should check for the gap between production online log and the log stream received by the standby database. This can be accomplished with v$managed_standby view.
The Total Block Gap between production and standby can be calculated this way:
Sum all blocks from v$archived_logs where seq# between Current Standby Seq# and Current Production Seq#. Then add current block# of the production LGWR process and subtract current block# from RFS standby process. This gives you total blocks even if there is a log sequence gap between sites.
This is NOT the gap of online log APPLIED to the standby database. THIS IS THE GAP OF ONLINE LOG TRANSMITTED TO THE STANDBY RFS PROCESS and can be used to monitor your dataguard transmission from production to disaster recovery environment.

This is an excerpt of such script (please take care that it does not check against RFS failures, so it can fails when RFS is not alive):

Any comment is appreciated!