However, Oracle has pretty much broken this mold in 12.1.0.2, which is not unexpected. Many of the new features in 12.1.0.2 revolve around adding normal database functionality that was not initially present in multitenant. In the first of my new features blog posts, let’s look at three of the new features present in the Oracle Database 12.1.0.2.
1. PDB CONTAINERS Clause
The CONTAINERS clause provides a way to address data in two or more PDB’s in a single query. Thus, if you have two EMP tables, and they are in PDB’s called AHR and RHR – you can now issue a select that accesses each table in the different PDB’s.For example, let’s say that we wanted to see the average cost of an employee’s benefit to the employer.In our case this information resides in two different systems. The active employee data is in the AHR PDB, the retiree data is sitting in the RHR database. If the employeer benefit cost for an employee is in a table called EMPLOYEE and the data is in a column called BENEFIT_COST, then we could query both tables using one SQL statement to get the average BENEFIT_COST. Here is an example:
SELECT avg(benefit_cost)
FROM CONTAINERS(HR.employee)
WHERE CON_ID IN (45, 49);
Note in this query that we have to list the CON_ID of the containers we want to include the query. We could slightly modify this query so we don’t need to know the CON_ID of the containers like this:
SELECT avg(benefit_cost)
FROM CONTAINERS(HR.employee)
WHERE CON_ID IN (select con_id in dba_containers
where con_name in (’AHR’,’RHR’) );
This is clearly a simpler solution.
2. CREATE_FILE_DEST parameter
If you have dealt with CDB’s and PDB’s you might get a little frustrated with the lack of ease with respect to the creation of PDB related datafiles. Originally in 12c Release 1 the database would put the files in the default file system directory and there was not an easy way to shortcut this default value.
This new functionality is facilitated through the use of the CREATE_FILE_DEST parameter. This parameter set unique to each PDB. Once defined, you will need to make sure that the mount point that is defined has been created and that the appropriate permissions are granted to Oracle so that it may read and write files to the file system.
Note that this parameter can be used to make plugging PDB’s in and out since the files will be isolated away from other PDB and CDB related files.
3.PDB Metadata CloneOracle’s ability to quickly clone a PDB is one big selling features of Multitennant. One of the nice features of 12.1.0.2 is the ability to clone a PDB with all the logical structures, but none of the data is cloned over. This is a nice feature if you need to fast provision a development database from a production source, but you don’t wish to put production data in that cloned database.
You might be asking yourself – Why do I care about CDBs and PDB’s anyway. We are not going to be using Oracle Multitennant anyway. My response is simple – yes, you will. Someday the Oracle infrastructure will be purely based on the concept of a Container Database and at least one Pluggable Database. So, you might as well get ready for that revolution now – because it is coming.
4.Force Full Database Caching ModeForce Full Database Caching Mode is new in Oracle 12.1.0.2. You might have heard about the Oracle In-memory database features that are being released with 12.1.0.2 (this feature is called the in-memory column store) – and you might have accidently confused this feature for the Oracle in-memory database features. These are two different features. I’ll address Oracle’s in-memory database features at a later date or you can read about them now on this page. You can enable Force Full Database Cashing Mode by mounting the database and then using the alter database force full database caching command and then open the database with the alter database open command. You only need to issue this command once and the database will continue to open in Force Full Database Caching Mode on subsequent database opens.
To turn off Force Full Database Caching Mode shutdown the database, mount it, and issue the command alter database no force full database caching. You can then open the database with the alter database open command.
More new feature stuff to come!