Oracle Database 12 c

ORACLE 12C : Listener service registration

With previous releases PMON (Process Monitor) was responsible for registering database services to the Listener. Starting from Oracle 12C there is a change in architecture with respect to the service registration in Oracle Database Release 12c. Oracle has introduced a new mandatory background process dedicated for “database service registration to the Listener” and named LREG (Listener Registration Process). The listener registration process (LREG) registers information about the database instance and dispatcher processes with the Oracle Net listener (see “The Oracle Net Listener”). When an instance starts, LREG polls the listener to determine whether it is running. If the listener is running, Read More

ORACLE 12C: Dataguard Far Sync

Oracle Dataguard Far Sync instance is a new feature introduced in Oracle Database 12c, which simply works like a archive/redo repeater.. Far sync instance is something different than the Oracle Database instance, as its mission is accepting redo from the primary database and then shipping that redo to other members of the Oracle Data Guard configuration.. Far Sync instance is an instance without a database.. Although; it has controlfile, and capability to read from standby redolog files and write them into its local archive log files, Far Sync instance does not map any database file, in other words, does not Read More

Create Sequence-Oracle Database 12c

Database version : from Oracle Database 12cR1 Create sequence with session or global option When a sequence number is generated, the sequence is incremented, independent of the transaction committing or rolling back. SESSION option makes opportunity to create sequence that can used in association with global temporary table then its visibility is just for session. The following options CACHE, NOCACHE, ORDER, or NOORDER are ignored when SESSION is declared. 1) statement SQL> CREATE GLOBAL TEMPORARY TABLE glb_tmp_table (a number); Table created. SQL> CREATE SEQUENCE sq_sess SESSION; Sequence created. 2) Script execution SQL> INSERT INTO glb_tmp_table VALUES (sq_sess.NEXTVAL); 1 row created. Read More

ORACLE 12 rel.2 – Partitioning new features

In Oracle 12c rel.2 a great number of enhancements to the Oracle database Partitioning option have been introduced. These include: Automatic List Partitioning Filtered Partition maintenance operations Multi-Column List Partitioning Online conversion of non-partitioned to partitioned table Read-only Partitions Partitioned External Tables Automatic List Partitioning: The ability to partition a table based on distinct values in a column has been around since quite some time, but what is new in Oracle database 12.2 is that we can initially partition the table based on values that are known and present in the column we would like to partition the table on. Read More

ORACLE 12C M.T.S. model

Until Oracle Database 12c, Oracle processes did not run as threads on UNIX and Linux systems. Every dedicated connection was represented by an operating system process. In systems where high workload was an issue, the only way to reduce CPU and memory usage was to switch from dedicated connections to shared connections using the multithreaded server (MTS) feature. Starting in Oracle Database 12c the multithreaded database model was introduced, enabling database processes to be executed as operating system threads and reducing the number of dedicated process necessary to manage database services. By default, every new 12c instance is created to Read More

Memory Resource Management for PDBs in Oracle Database 12c Rel.2 (12.2)

In the previous release there was no way to control the amount of memory used by an individual PDB. It could use up lots of memory and impact the performance of other PDBs in the same instance. Oracle Database 12c Rel.2 (12.2) allows to control the amount of memory used by a PDB. PDB Memory Parameters The following parameters can be set at the PDB level. DB_CACHE_SIZE : minimum buffer cache size for the PDB. SHARED_POOL_SIZE : minimum shared pool size for the PDB. PGA_AGGREGATE_LIMIT : maximum PGA size for the PDB. PGA_AGGREGATE_TARGET : target PGA size for the PDB. Read More