NEW IN ORACLE12C AND ORACLE18C
Oracle12c R2 Multitenant Container Database Architecture
Oracle12c R2 Database Architecture
The following are changes in the Oracle Multitenant option documentation for Oracle Database 12c Release 2 (220.127.116.11).
The following features are new in this Oracle12c second release:
- Application containers
An application container is an optional component of a multitenant container database (CDB) that consists of an application root and the application PDBs associated with it. An application container stores data for one or more applications.
- Application common objects
Besides, application common objects are created in an application root and are shared with the application PDBs that belong to the application root.
- Support for thousands of pluggable databases (PDBs) in a single CDB
A CDB can contain up to 4,096 PDBs; oh, what a great improvement!
- Use different character sets for PDBs
When the character set of the CDB root is AL32UTF8, any container in the CDB can use a character set that is different from the CDB root and different from other containers in the CDB, which is great for multiple deployment of website content for localization and globalization purposes as appropriate.
- Relocate a PDB from one CDB to another
A PDB can be easily relocated in one operation with minimal down time.
- Proxy PDB
Indeed, a proxy PDB references a PDB in a different CDB and provides fully functional access to the referenced PDB, which represents a fundamental improvement.
- Hot PDB cloning
Now, the source PDB can be in open read/write mode during a PDB clone operation.
- Rename services during PDB creation
Similarly, the SERVICE_NAME_CONVERT clause of the CREATE PLUGGABLE DATABASE statement renames the user-defined services of the new PDB based on the service names of the source PDB.
- Switch to a specific service for a container in a CDB
The DBA can specify a service name in an ALTER SESSION SET CONTAINER statement.
- Manage the memory usage of PDBs in a CDB
The DBA can configure guarantees and limits for SGA and PGA memory, using PDB initialization parameters.
- Limit the I/O generated by specific PDBs
Conveniently, two new initialization parameters, MAX_IOPS and MAX_MBPS, enable the administrator to limit disk I/O generated by a PDB. MAX_IOPS limits the number of I/O operations, and MAX_MBPS limits the megabytes for I/O operations.
- PDB performance profiles
The DBA can specify Resource Manager directives for a set of PDBs using PDB performance profiles.
- Monitor PDBs managed by Oracle Database Resource Manager
A set of dynamic performance views enables an administrator to monitor the results of his Oracle Database Resource Manager settings for PDBs.
- Prioritize PDB upgrades
The DBA can prioritize the PDBs in a CDB when he upgrades the CDB. The PDBs with higher priority are upgraded before PDBs with lower priority.
- CDB undo mode
A CDB can run in local undo mode or shared undo mode. Local undo mode means that every container in the CDB uses local undo. Shared undo mode means that there is one active undo tablespace for a single-instance CDB. For an Oracle RAC CDB, there is one active undo tablespace for each instance.
- Parallelized PDB creation
The PARALLEL clause of the CREATE PLUGGABLE DATABASE statement specifies whether to use parallel execution servers during PDB creation and, optionally, the degree of parallelism.
- Unplugging PDBs and plugging in PDBs with an archive file
A PDB can be unplugged into compressed archive of the XML file that describes the PDB and the files used by the PDB (such as the data files and wallet file). The archive file has a .pdb extension, and it can be used to plug the PDB into a CDB or application container.
- PDB refresh
The DBA can create a PDB as a refreshable clone and refresh the PDB with changes made to the source PDB.
- Improved support for default tablespace specification during PDB creation
The DBA can specify a default tablespace for a PDB that is created using techniques such as cloning and plugging in the PDB. Previously, a default tablespace could be specified only if the PDB was created from PDB$SEED.
- Extended USER_TABLESPACES clause during PDB creation
The creation mode of user tablespaces can be different than the creation mode of the PDB. For example, during PDB creation, the user tablespaces can move a tablespace’s files even when file copy is specified for the PDB.
The following are changes in the Oracle Multitenant option for Oracle Database 12c Release 1 (18.104.22.168).
The following features are new in this release:
- Preserving the open mode of PDBs when the CDB restarts
Off course, the administrator can preserve the open mode of one or more PDBs when the CDB restarts by using the ALTER PLUGGABLE DATABASE SQL statement with a pdb_save_or_discard_state clause.
- The USER_TABLESPACES clause of the CREATE PLUGGABLE DATABASE statement
An administrator can use this clause to separate the data for multiple schemas into different PDBs. For example, assume that each schema in a non-CDB uses a separate tablespace. When the DBA moves a non-CDB to a PDB, and when the non-CDB has schemas that supported different applications, he can use this clause to separate the data belonging to each schema into a separate PDB,
- Excluding data when cloning a PDB
The NO DATA clause of the CREATE PLUGGABLE DATABASE statement specifies that a PDB's data model definition is cloned but not the PDB's data.
- Default Oracle Managed Files file system directory or Oracle ASM disk group for a PDB's files
The CREATE_FILE_DEST clause specifies the default location.
- Create a PDB by cloning a non-CDB
The DBA can create a PDB by cloning a non-CDB with a CREATE PLUGGABLE DATABASE statement that includes the FROM clause.
- The logging_clause of the CREATE PLUGGABLE DATABASE and ALTER PLUGGABLE DATABASE statement
This clause specifies the logging attribute of the PDB. The logging attribute controls whether certain DML operations are logged in the redo log file (LOGGING) or not (NOLOGGING).
- The pdb_force_logging_clause of the ALTER PLUGGABLE DATABASE statement
This clause places a PDB into force logging or force nologging mode or takes a PDB out of force logging or force nologging mode.
- The STANDBYS clause of the CREATE PLUGGABLE DATABASE statement
This clause specifies whether the new PDB is included in standby CDBs.
- Querying user-created tables and views across all PDBs
The CONTAINERS clause enables administrators to query user-created tables and views across all PDBs in a CDB.
Oracle18c Release 1 Database SGA (basic view)
The following are changes to be highlited in Oracle 18c Multitenant, release 22.214.171.124.
The newly established CDB fleet [concept] is a collection of different CDBs that can be managed as one logical CDB.
- PDB snapshot carousel
A PDB snapshot is a point-in-time copy of a PDB. Thus, when a PDB is enabled for snapshots, the administrator can create multiple snapshots (point-in-time copies) of the PDB. The library of snapshots is called a PDB snapshot carousel. The DBA can quickly clone a new PDB based on any snapshot in the carousel. In this way, the DBA can perform point-in-time recovery to any snapshot in the carousel, or rapidly create a PDB by cloning any snapshot.
- Logical partitioning
A container map enables a session to issue SQL statements that are routed to the appropriate PDB, depending on the value of a predicate used in the SQL statement. Indeed, the partitioning column in the map table does not need to match a column in the metadata-linked table. For example, if the table sales is enabled for the container map pdb_map_tbl, and if sales does not have the column used to partition pdb_map_tbl, then queries with the predicate CONTAINERS(sales) are still routed to the PDBs specified in the map table.
- Refreshable PDB switchover
A refreshable clone PDB is a read-only clone that can periodically synchronize with its source PDB. The DBA can reverse the roles, transforming the source PDB into the clone and the clone into the source. This technique can be useful for load balancing. Also, if the source PDB fails, then administrators can resume operations on the clone PDB, rendering a CDB-level Oracle Data Guard failover unnecessary.
- Lockdown profile enhancements
The DBA can create, alter, or drop lockdown profiles in application containers. Also, administrators can create lockdown profiles based on a static or a dynamic base profile.
- DBCA enhancements
The DBA can use DBCA to clone a local PDB or duplicate a CDB. Duplication is only supported in silent mode.
- Usable backups of non-CDBs and relocated PDBs
When administrators are cloning a non-CDB as a PDB or relocating a PDB, the DBA can use the DBMS_PDB.EXPORTRMANBACKUP procedure to export RMAN backup metadata into the PDB dictionary. This metadata enables backups of the source non-CDB or PDB to be usable for restore and recovery of the target PDB.
- RMAN duplication of a PDB to another CDB
The DBA can clone a PDB from a source CDB to an existing CDB that is open read/write.
- Relocation of sessions during planned maintenance
Application Continuity can drain database sessions during planned maintenance when the application submits a connection test, at request boundaries, and at good places to fail over. The relocation is transparent to applications. This feature is on by default for all maintenance operations invoked at the database service and PDB levels: stop service, relocate service, relocate PDB, and stop PDB..
- Copying a PDB in an Oracle Data Guard environment
Suitably, when performing a remote clone in a primary database, or plugging in a PDB in a primary database, administrators can set initialization parameters in a standby database that automates copying the data files for the newly created PDB.
- Parallel statement queuing at the PDB level
A DBA can configure parallel statement queuing for a PDB just as for a non-PDB using the PARALLEL_SERVERS_TARGET initialization parameter. At the PDB level, the default is based on the CPU_COUNT setting for the PDB. In contrast, at the CDB level, the default value is the value of the PARALLEL_MAX_SERVERS initialization parameter.
- Split mirror clone PDBs
When a PDB resides in Oracle ASM, administrators can use a split mirroring technique to clone a PDB. The cloned PDB is independent of the original PDB. The principal use case is to rapidly provision test and development PDBs in an Oracle ASM environment.