some of the characteristics of a CDB

some of the characteristics of a CDB

• There is a separate SYSTEM and SYSAUX tablespace for the root container of the CDB and each PDB
• Thee is only one UNDO tablespace for the entire CDB
• There is only one set of control files and online redo logs files for the entire CDB. Individual PDB’s have their own data files (which contain the user data), but do not have distinct redo log or control files.
• We can create on default temporary tablespace for the entire CDB or each PDB can have its own additional temporary tablespaces
• There is single network administration files like listener.ora, tnsnames.ora, and sqlnet.ora file for an entire CDB. All of the PDBs in the CDB use the same files.
• There is only one set of background processes shared by the root and all PDBs
• There is a single SGA shared by all  PDB’s
• When the CDB is shut down then all PDB’s are also automatically shut down
• When the CDB is open then we can change the open mode of individual PDBs via the ALTER PLUGGABLE DATABASE SQL statement.

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Oracle Database 12c: INTERACTIVE QUICK REFERENCE

http://www.oracle.com/webfolder/technetwork/tutorials/obe/db/12c/r1/poster/OUTPUT_poster/poster.html#tab_1

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Oracle Database 12c was officially released  and is now available for download. Along with the software release comes a whole new set of collateral that explains in detail all of the new features and functionality you will find in this release.

The Optimizer page on Oracle.com has all the juicy details about what you can expect from the Optimizer in Oracle Database12c.  There you will find the following 3 new white papers;

• What to expect from the Oracle Optimizer in Oracle Database 12c
• SQL Plan Management with Oracle Database 12c
• Understanding Optimizer Statistics with Oracle Database 12c
• Best Practices For Gathering Optimizer Statistics with Oracle Database 12c

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     CHANGE VARCHAR2 TO 32K – 12C 

Oracle has made a few changes to the database to allow organizations to reduce the cost of migrating to Oracle 12c.  One of these changes is with the size limits that have been placed on the VARCHAR2, NVARCHAR2 and RAW data types.  In past versions of Oracle database the maximum size for these data types were 4,000 bytes.  In Oracle 12c, these data types can now  be increased to 32,767 bytes.

In order to set these data types to use the larger setting, the MAX_STRING_SIZE parameter needs to be set.  The only values that this parameter can take is STANDARD and EXTENDED.  Once the parameter has been set to EXTENDED, you cannot go back to STANDARD.

Note: Altering MAX_STRING_SIZE will update database objects and possibly invalidate them

To increase the size of the VARCHAR2, NVARCHAR2 and RAW columns for a non-CDB database,  these steps need to be followed: 

                  1. Shutdown the database

                  2. Restart in UPGRADE mode

                  3. Change the setting of MAX_STRING_SIZE to EXTENDED

                  4. Run $OH/rdbms/admin/utl32k.sql  <- must be connected as SYSDBA

                  5. Restart in NORMAL mode.

The same procedure can be followed and applied against an Oracle PDB, Oracle RAC database, Oracle Data Guard Logical Standby Databases.  

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