This preface contains:
Oracle Database Concepts for Oracle Database 12c Release 2 (188.8.131.52) has the following changes.
The following major features are new in this release:
Oracle Database Sharding
Oracle Sharding is a scalability and availability feature for suitable OLTP applications in which data is horizontally partitioned across discrete Oracle databases, called shards, which share no hardware or software. An application sees the collection of shards as a single logical Oracle database. Sharding provides linear scalability with fault isolation, automation of many lifecycle management tasks, excellent runtime performance, and the many advantages that come using an Oracle database as a shard (such as SQL and JSON support) .
See "Oracle Sharding Architecture".
An application container consists of an application root and one or more application PDBs. The container stores data for a specific application, which contains common data and metadata. You can upgrade or patch the application once in the application root, and then synchronize the application PDBs with the root.
PDB creation and relocation enhancements
These enhancements include:
You can relocate a PDB from one CDB to another with minimal down time (see "Creation of a PDB by Relocating").
During a PDB clone operation, the source PDB no longer needs to be in read-only mode (see "Creation of a PDB by Cloning a PDB or a Non-CDB").
You can create a proxy PDB, which references a PDB in a different CDB and provides fully functional access to the referenced PDB ("Proxy PDBs").
Flashback PDB and PDB restore points
You can use
FLASHBACK PLUGGABLE DATABASE command to rewind a PDB to any SCN without affecting other PDBs in a CDB. You can also create a restore point specific for a PDB, and rewind the PDB to this restore point without affecting other PDB.
PDB lockdown profiles
A PDB lockdown profile is a security mechanism to restrict operations that are available to users connected to a specified PDB. For example, a CDB administrator might create a lockdown profile to restrict networking access such as
UTL_SMTP, or local user access to objects in a common schema.
Performance manageability enhancements
You can configure PDB parameters to guarantee or limit SGA memory, PGA memory, sessions, CPU, and I/O rates for each PDB. You can also configure performance profiles to configure Oracle Database Resource Manager resource plans for a large number of PDBs.
Advanced index compression enhancements
Advanced high compression (
COMPRESS ADVANCED HIGH) offers higher ratios than index compression offered in previous releases.
See "Advanced Index Compression".
Hybrid Columnar Compression (HCC) extended to conventional inserts
Conventional inserts into heap-organized tables can use Hybrid Columnar Compression. Thus, the compression benefits now extends to
SQL INSERT SELECT statements without the
APPEND hint, and array inserts from programmatic interfaces such as PL/SQL and the Oracle Call Interface (OCI).
You can partition external tables on virtual or non-virtual columns. Thus, you can take advantage of performance improvements provided by partition pruning and partition-wise joins. Oracle Database also provides the
ORACLE_HDFS driver for the extraction of data stored in a Hadoop Distributed File System (HDFS), and the
ORACLE_HIVE driver for access to data stored in an Apache Hive database.
See "Overview of External Tables".
List partitioning is expanded to allow multiple partition key columns.
See "List Partitioning".
Unstructured data enhancements
Oracle Database extends support for storing and querying JSON documents in the database by enabling you to generate JSON documents from relational data using SQL and manipulate JSON documents as PL/SQL objects. Also, the IM column store now loads an efficient binary representation of JSON columns.
Oracle Multimedia PL/SQL API
Oracle Multimedia provides a PL/SQL API for multimedia functionality such as image thumbnail creation, image watermarking, and metadata extraction for multimedia data stored in BLOBs and BFILEs.
Local temporary tablespaces
You can create local, nonshared temporary tablespaces. When many read-only instances access a single database, local temporary tablespaces can improve performance for queries that involve sorts, hash aggregations, and joins.
In previous releases, the term temporary tablespace referred to what is now called a shared temporary tablespace.
See "Temporary Tablespaces".
Application Continuity enhancements
Application Continuity for planned outages enables applications to continue operations for database sessions that can be reliably drained or migrated. An application-independent infrastructure enables continuity of service from an application perspective, masking planned outages relating to the database.
Real-Time database operation monitoring enhancements
You can start and stop a database operation from any session in the database by specifying the session identifier and serial number for a particular session.
See "Database Operations".
Instance architecture enhancements
Support for read/write and read-only instances in the same database
Both read/write and read-only instances can open the same database. Read-only instances improve scalability of parallel queries for data warehousing workloads. For example, in an
INSERT ... SELECT statement, the read/write and read-only instances process the
SELECT, whereas only the read/write instances process the
You can pre-create a pool of server processes by using the
DBMS_PROCESS PL/SQL package. The new Process Manager (PMAN) background process monitors the pool of pre-created processes, which wait to be associated with a client request. When a connection requires a server process, the database can eliminate some of the steps in process creation.
Process Monitor (PMON) process group
Duties that belonged exclusively to PMON now belong to the PMON process group, which includes PMON, Cleanup Main Process (CLMN), and Cleanup Helper Processes (CLnn). The PMON process group is responsible for the monitoring and cleanup of other processes.
Database resource quarantine
In some cases, process cleanup itself can encounter errors, which can result in the termination of process monitor (PMON) or the database instance. In some circumstances, by allowing certain database resources to be quarantined, the database instance can avoid termination.
See "Database Resource Quarantine".
Optimizer Statistics Advisor
This built-in diagnostic software analyzes how you are currently gathering statistics, the effectiveness of existing statistics gathering jobs, and the quality of the gathered statistics. Optimizer Statistics Advisor maintains rules, which embody Oracle best practices based on the current feature set. In this way, the advisor always provides the most up-to-date recommendations for statistics gathering.
See "Optimizer Statistics Advisor".
Oracle Database Concepts for Oracle Database 12c Release 1 (184.108.40.206) has the following changes.
The following features are new in this release:
In-Memory Column Store
The In-Memory Column Store (IM column store) is an optional area in the SGA that stores whole tables, table partitions, and individual columns in a compressed columnar format. The database uses special techniques, including SIMD vector processing, to scan columnar data rapidly. The IM column store is a supplement to rather than a replacement for the database buffer cache.
See "In-Memory Area".
Automatic Big Table Caching
This optional, configurable portion of the database buffer cache uses an algorithm for large tables based on object type and temperature. In single-instance and Oracle RAC databases, parallel queries can use the big table cache when the
DB_BIG_TABLE_CACHE_PERCENT_TARGET initialization parameter is set to a nonzero value, and
PARALLEL_DEGREE_POLICY is set to
adaptive. In a single-instance configuration only, serial queries can use the big table cache when
DB_BIG_TABLE_CACHE_PERCENT_TARGET is set.
Oracle Database Concepts for Oracle Database 12c Release 1 (220.127.116.11) has the following changes.
The following features are new in this release:
The multitenant architecture capability enables an Oracle database to function as a multitenant container database (CDB). A CDB includes zero, one, or many customer-created pluggable databases (PDBs). A PDB is a portable collection of schemas, schema objects, and nonschema objects that appears to an Oracle Net client as a non-CDB. You can unplug a PDB from a CDB and plug it into a different CDB.
Multiprocess and multithreaded Oracle Database
Starting with this release, Oracle Database may use operating system threads to allow resource sharing and reduce resource consumption.