Tag Archives: oracle database 12c

Oracle Database on ACFS: a perfect marriage?

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Update: I will give this presentation at UKOUG Tech15, Wed 9 December at 14:30.

This presentation has had a very poor score in selections for conferences (no OOW, no DOAG) but people liked it very much at Paris Oracle Meetup.  The Database on ACFS is mainstream now, thanks to the new ODA releases. Having some knowledge about why and how you should run (not) Databases on ACFS is definitely worth a read.

Slides

Demo 1 recording

Demo 2 recording

Demo script (DB ACFS clone from Standby Database)

 

Comments are, as always, very appreciated 🙂

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Ludo

It’s confirmed. Standard Edition and Standard Edition One are dead.

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The first voices came on July 3rd, 2015.

After many years of existence, Standard Edition and Standard Edition One will no longer be part of the Oracle Database Edition portfolio.

The short history

Standard Edition has been for longtime the “stepbrother” of Enterprise Edition, with less features, no options, but cheaper than EE. I can’t remember when SE has been released. It was before 2000s, I guess.

In 2003, Oracle released 10gR1. Many new features as been released for EE only, but:

– RAC as been included as part of Standard Edition

– Standard Edition One has been released, with an even lower price and “almost” the same features of Standard Edition.

For a few years, customers had the possibility to get huge savings (but many compromises) by choosing the cheaper editions.

SE ONE: just two sockets, but with today’s 18-core processors, the possibility to run Oracle on 36 cores (or more?) for less than 12k of licenses.

SE: up to four sockets and the possibility to run on either 72 core servers or RAC composed by a total of 72 cores (max 4 nodes) for less than the price of a 4-core Enterprise Edition deployement.

In 2014, for the first time, Oracle released a new Database version (12.1.0.2) where  Standard Edition and SE One were not immediately available.

For months, customers asked: “When will the Oracle 12.1.0.2 SE be available?”

Now the big announcement: SE and SE One will no longer exist. With 12.1.0.2, there’s a new Edition: Oracle Database Standard Edition 2.

You can find more information here:

 

Some highlights

– SE One will no longer exist

– SE is replaced by SE Two that has a limitation of 2 sockets

– SE Two still has RAC feature, with a maximum of two single-socket servers.

– Customers with SE on 4 socket nodes (or clusters) will need to migrate to 2 socket nodes (or clusters)

– Customers with SE One should definitely be prepared to spend some money to upgrade to SE Two, which comes at the same price of the old Standard Edition. ($17,500 per socket).

– the smallest amount of NUP licenses when licensing per named users has been increased to 10 (it was 5 with SE and SE One).

– Each SE2 Database can run max 16 user threads (in RAC, max 8 per instance). This is limited by the database Resource Manager. It does not prevent customers from using all the cores, in case they want to deploy many databases per server.

 

So, finally, less scalability for the same pricetag.

Other bloggers have already written about the behaviour of SE2. The best blog post is IMO from Franck Pachot. http://blog.dbi-services.com/oracle-standard-edition-two/

Cheers

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Ludo

SQL Plan Directives: they’re always good… except when they’re bad!

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The new Oracle 12c optimizer adaptive features are just great and work well out of the box in most cases.

Recently, however,  I’ve experienced my very first problem with SQL Plan Directives migrating a database to 12c, so I would like to share it.

Disclaimer 1: this is a specific problem that I found on ONE system. My solution may not fit with your environment, don’t use it if you are not sure about what you’re doing!

Disclaimer 2: despite I had this problem with a single SPD, I like adaptive features and I encourage to use them!!

Problem: a query takes a sub-second in 11gR2, in 12c it takes 12 seconds or more.

V_TAB_PROP is a very simple view. It just selects a central table “TAB” and then takes different properties by joining  a property table “TAB_PROP”.

To do that, it does 11 joins on the same property table.

On the property table, TAB_PROP_ID and PROP_ID are unique (they compose the pk), so nested loops and index unique scans are the best way to get this data.
The table is 1500Mb big and the index 1000Mb.

This was the plan in 11g:

In 12c, the plan switches to adaptive, and half of the joins are converted to hash joins / full table scans:

However, the inflection point is never reached. The execution keeps the default plan that has half of the joins HJ and the other half NL.

The problem in this case is the SQL Directive. Why?

There are to many distinct values for TAB_ID and the data is very skewed.

The histogram on that column is OK and it always leads to the correct plan (with the adaptive features disabled).
But there are still some “minor” misestimates, and the optimizer sometimes decides to create a SQL Plan directive:

The Directive instructs the optimizer to do a dynamic sampling, but with a such big and skewed table this is not ok, so the Dynamic sampling result is worse than using the histogram. I can check it by simplifying the query to just one join:

What’s the fix?

I’ve tried to drop the directive first, but it reappears as soon as there are new misestimates.
The best solution in my case has been to disable the directive, an operation that can be done easily with the DBMS_SPD package:

I did this on a QAS environment.
Because the production system is not migrated to 12c yet, it’s wise to import these disabled directives in production before the optimizer creates and enables them.

Off course, the directives can’t be created for objects that do not exist, the import  has to be done after the objects migrate to the 12c version.

Because the SQL Plan Directives are tied to specific objects and not specific queries, they can fix many statements at once, but in case like this one, they can compromise several statements!

Monitoring the creation of new directives is an important task as it may indicate misestimates/lack of statistics on one side or execution plan changes on the other one.

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

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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!

 

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Ludovico

Speaker and Ninja at Collaborate14 – #C14LV

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COLLABORATE 14 IOUG Forum

This year I will have the honor to present at Collaborate14, from April 7th to 11th. First of all, many thanks to Trivadis that has kindly agreed to send me to the conference.

My session (#603):
Oracle Data Guard 12c: Real-Time Cascade, Far Sync Instances and other goodies
has been accepted, so if you plan to attend Collaborate, I will be glad to see you there!
My paper and presentation are ready, but I’ll wait the post-conference before publishing them. Meanwhile, you can get a little sneak peak of my live demo (I’ll cut something, somewhere, but my new SSD disk should reduce the time elapsed, I have to do it again with the new hardware to get correct timings 🙂 ). There’s no audio, since it’s supposed to be my failover demo if I’ll have problems during my session.

Part I


Part II

I’ve submitted another abstract about Policy Managed Databases, but it has been put in the waiting list, assuming that Data Guard has a lot more users and the interest in new Data Guard 12c features will be higher than PMDBs that are rarely used in production environments (and I’m sad about it, keep in touch if you want to know more about this great technology).

 

RAC Attack 12c!

I’ll be organizing the RAC Attack again, along with Seth Miller, Yury Velikanov and Kamran Agayev. Sharing this exciting role with an Oracle ACE and two ACE Directors makes me  proud of what I’m doing, but more than this, I’m happy to repeat another exciting experience like I had at OOW13.

This Year RAC Attack will be an official pre-conference workshop. We have been contacted directly by the IOUG, and we’re making improvements. We’ll install RAC 12c and discuss about advanced topics, have a lot of fun, drink a beer together and jump a lot! 🙂

Other mentors at the workshop will be Leighton Nelson, Maaz Anjum, Biju Thomas. You should know them already, so join us!

And don’t forget, register before February 12th, so you take benefit of the early bird discount!

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Ludovico

Playing with Oracle 12c Multitenant Users and Roles

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I’ve realized these days that the great list of articles by Oracle Alchemist does not contain any articles describing a little more in depth common roles and Users.

I’ve found these ones by Pete Finnigan and Bobby Curtis:

http://www.petefinnigan.com/weblog/archives/00001366.htm

http://dbasolved.com/2013/06/29/common-user-vs-local-user-12c-edition/

http://www.petefinnigan.com/weblog/archives/00001370.htm

But I would like to investigate a little more.

My test environment

Just to give you an idea, I have two PDBs (HR and HR2), each containing an HR schema.

Creating the common user

As already pointed by the existing articles, I can’t create a common user into the root container without the c## prefix, unless I’m altering the hidden parameter _common_user_prefix.

so I specify the correct prefix, and it works:

The user is common, so it appears in all the containers, I can check it by querying CDB_USERS from the root container.

Creating the local user

Then I create also a local user into the HR PDB.

 

CDB_USERS scope

From the PDB I see only the users in the PDB scope:

If I change to the root, I see the users valid into all the containers:

Creating a common role

Do the roles obey to the same rules valid for the users?

Yes, they do! So, let’s create a common role with the C## prefix:

It works, but if I try to create a common role into the root container only, I get an error:

And also if I try to create a local role into the root, I can’t:

Note that the error ORA-65049 is different from the ORA-65096 that I’ve got before.

My conclusion is that the clause container of the create role and create user statements doesn’t make sense as you can ONLY create common users and roles into the root container and only local ones into the PDBs.

 Creating a local role

Just as experiment, I’ve tried to see if I can create a local role with container=ALL. It doesn’t work:

So I create the local role with container=current:

Now, from the PDB I can see the two roles I can access, whereas from the root I can see all the roles I’ve defined so far: the common role is available from all the PDBs, the local role only from the db where it has been defined, just like the users.

 Granting object privileges to the roles

From the root I can’t give grants on objects that reside in a PDB since I cannot see them: I need to connect to the PDB and give the grants from there:

Now, if I query CDB_TAB_PRIVS from the root, I see that the grants are given at a local level (con_id=3 and common=N):

 Granting common and local roles to commond and local users

From a PDB, I can grant local roles to local users or common users:

But I can’t grant a common role to a common user with container=all if I’m in a PDB:

To grant the a common role to a common user I can decide either to:

  •  give the grant locally while connected to the PDB:

  •  give the grant commonly while connected to the root:

I can also grant locally both roles and system privileges to common users while connected to the root container: in this case the privileges are applied to the root container only. Finally having the clause container finally starts to make sense:

Verifying the grants

Ok, I’ve given the grants and I’ve never verified if they work, so far.

Let’s try with the select any table privilege I’ve given in the last snippet. I expect C##GOOFY to select any table from the root container and only HR.COUNTRIES and HR.REGIONS on the HR PDB bacause they have been granted through the two roles.

What’s the mess? When I’ve created the user c##goofy, I’ve granted create and alter session without the container=all:

According to the documentation, the grant command uses container=current by default (common=N):

So, I need to give the grants commonly to let c##goofy connect to all the PDBs:

Now I see that the grants give two distinct permissions : one local and the other common.

If I revoke the grants without container clause, actually only the local one is revoked and the user can continue to login. To revoke the grants I would need to check and revoke both local and common privileges.

After the first revoke statement, I can still connect to HR and verify that my select any table privilege doesn’t apply to the PDB as it’s local to the root container:

After that, I want to check the privileges given through the local and common roles.

I expect both users to select from hr.countries and hr.regions since they have been granted indirectly by the roles.

Let’s try the local user first:

Yeah, it works as expected.

Now let’s try the common user:

It also work, so everything is ok.

Common and local grants, why you must pay attention

During the example, I’ve granted the C##COUNTRY_ROLE many times: locally to PDB, locally to the ROOT, commonly. The result is that I’ve flooded the grant table with many entries:

Let’s try to clean things: for sure I don’t need the grant local to the root:

Then I can choose between revoking the common privilege or the local one. Let’s try to remove the local one:

I’ve removed the local one, but I have still the common one (I’m connected to the PDB so the entries from the other containers are not displayed):

I still have access to the tables as expected:

So, you must pay attention to a couple of things:

  • When granting privileges from the root container, keep in mind that container=current is the default even when the grantee or the role granted are common.
  • When revoking the grants with a Multitenant architecture, keep in mind that there is a scope and you may need more than one statement to actually remove the grant from all the scopes.

As always, I look for opinions and suggestions, feel free to comment!

🙂

—
Ludovico

How many Oracle instances can be consolidated on a single server?

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According to Exadata consolidation guide, this is what you can consolidate on Oracle specialized Hardware:

NOTE: The maximum number of database instances per cluster is 512 for Oracle 11g Release 1 and higher. An upper limit of 128 database instances per X2-2 or X3-2 database node and 256 database instances per X2-8 or X3-8 database node is recommended. The actual number of database instances per database node or cluster depends on application workload and their corresponding system resource consumption.

 

But how many instances are actually beeing consolidated by DBAs from all around the world?

I’ve asked it to the Twitter community

I’ve sent this tweet a couple of weeks ago and I would like to consolidate some replies into a single blog post.

 

My customer environment however, was NOT a production one. On the production they have 45.

Some replies…

 

 

 

Wissem cores 73 on a production system, 1TB memory!

 

Chris correctly suggests to give a try to the new 12c consolidation features:

 

Kevin, as a great expert, already experimented one hundred instances environment:

But Bertrand impresses with his numbers!

 

 

 

 

 

Intel platform with 1TB of RAM = Xeon E7, suggests Kevin:

 

 

 

Flashdba has seen 87 instances on a single host, but on a Multi-node RAC: but still huge and complex!

 

 

 

Conclusion

Does this thread of tweets reply to the question? Are you planning to consolidate your Oracle environment? If you have questions about how to plan your consolidation, don’t hesitate to get in touch! 🙂

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Ludo

Oracle Database 12c: Multitenant, Services and Standard Edition RAC

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The installation process of a typical Standard Edition RAC does not differ from the Enterprise Edition. To achieve a successful installation refer to the nice quick guide made by Yury Velikanov and change accordingly the Edition when installing the DB software.

Standard Edition and Feature availability

The first thing that impressed me, is that you’re still able to choose to enable pluggable databases in DBCA even if Multitenant option is not available for the SE.

So I decided to create a container database CDB01 using template files, so all options of EE are normally cabled into the new DB. The Pluggable Database name is PDB01.

As you can see,  the initial banner contains “Real Application Clusters and Automatic Storage Management options“.

Multitenant option is not avilable. How SE reacts to its usage?

First, on the ROOT db, dba_feature_usage_statistics is empty.

This is interesting, because all features are in (remember it’s created from the generic template) , so the feature check is moved from the ROOT to the pluggable databases.

On the local PDB I have:

Having ONE PDB is not triggering the usage of Multitenant (as I was expecting).

How if I try to create a new pluggable database?

A-AH!! Correctly, I can have a maximum of ONE pluggable database in my container.

This allows however:

  • Smooth migration from SE to a Multitenant Architecture
  • Quick upgrade from one release to another

To be sure that I can plug/unplug, I’ve tried it:

Other features of Enterprise off course don’t work

Create a Service on the RAC Standard Edition (just to check if it works)

I’ve just followed the steps to do it on an EE. Keep in mind that I’m using admin managed DB (something will come about policy managed DBs, stay tuned).

As you can see it works pretty well. Comparing to 11g you have to specify the -pdb parameter:

Then I can access my DB (and preferred instance) using the service_name I specified.

 

Let me know what do you think about SE RAC on 12c. It is valuable for you?

I’m also on twitter: @ludovicocaldara

Cheers

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Ludo

Oracle Database 12c: RMAN recover at table level

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Brett Jordan David MacdonaldOracle Database 12c comes with a new feature named “RMAN table level recovery”.

After a quick try it’s easy to understand that we are talking about Tablespace Point-in-Time Recovery (TSPITR) with some automation to have it near-transparent.

 

How to launch it

The syntax is quite trivial. Suppose you’ve dropped a table ludovico.reco and then purged it (damn!) then you can’t flashback it to before drop and don’t want to flashback the entire database.

 

You can recover the table with:

 

You identify the schema.table:partition to restore, optionally you can pass the pluggable database containing the table to recover, the time definition as usual (scn, seq# or timestamp) and an auxiliary destination.

This Auxiliary destination is well-known to be mandatory for TSPITR. You can pass other options like table renaming or tablespace remapping.

Off course, the database must be open in read-write, in archivelog mode and at least one successful backup must be taken.

How it works

Oracle prepare an auxiliary instance by restoring the SYSTEM, UNDO and SYSAUX tablespaces.

Then it opens in READ-ONLY mode the partial database.

 

It uses then the read-only dictionary to take the tablespace that was containing the table before the data loss. This tablespace (users in my example) is restored and recovered, and the database is opened.

 

At this  point, RMAN starts an export/import with datapump to move the table from the auxiliary database back to the target database:

 

Finally, the auxiliary instance is cleaned:

 

We can check if our table is ok:

 

Oh, and yes, now we can select directly from RMAN! 🙂

 

 My opinion

  • It still needs the amount of space needed to recover the auxiliary instance (system, sysaux, temp and the user tablespace containing the missing data), so it has all the defeats of the typical TSPITR, but it’s automatic so is an improvement for the real life.
  • Restoring the user tablespace separately from the system tablespaces can be an issue if you’re saving backupsets over tape: you can end up by reading twice the same backupset that could be read once instead.

Cheers

Ludovico

Oracle Database 12c: sequence.nextval as default and identity columns

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Finally! I can count how many times I’ve seen questions like this one.

The new Oracle 12c now allows to define a table with the sequence.nextval directly in the in-line column definition:

 

But Oracle has fixed this twice, in the new release it’s possible to use identity columns as well, avoiding the necessity to create explicitly a new sequence:

I’ve said “explicitly” because actually a sequence is created with a system-generated name, so you’ll still need to deal with sequences.

 

cheers

Ludo