ENGEBEYAY

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Description

Here are some of the rest new features of 12c compared to 11g:

 

1\.Multiple indexes

 

Before Oracle users were able to create a single index on one column\. With Oracle 12c users can create multiple indexes on the same column\. However, the index type must be different and only one type of index is visible at a given time\.

 

2\.Invisible columns

 

Oracle 12c introduces new feature of invisible columns in the table\. When a user defines a column as invisible, it won’t appear in generic queries, unless the column is explicitly referred to in the SQL statement or condition, or described in the table definition\. However, temporary tables, external tables and cluster tables won’t support invisible columns\.

 

3\.In-memory aggregation

 

Oracle 12C supports In-memory aggregation, which optimizes the queries that joins the dimension tables to fact tables and aggregate data\. User needs to use KEY VECTOR and VECTOR GROUP BY operations to achieve the In-memory aggregation\. In memory, aggregation is used in star schema, which improves the performance of Star queries and reduces the CPU usage\. The In-memory aggregation eliminates the need of summary tables in most of cases which simplifies the star schema query\.

 

4\.JSON Support

 

This feature adds support for storing, querying and indexing JavaScript Object Notation \(JSON\) data to Oracle Database\. It allows the database to enforce that JSON stored in the Oracle Database conforms to the JSON rules\. This feature also allows JSON data to be queried using a PATH based notation and adds new operators that allow JSON PATH based queries to be integrated into SQL operations\.

 

5\.Automatic Big table caching:

 

In previous versions of Oracle, in-memory parallel query did not work well when multiple scans contended for cache memory\. The new cache mechanism called big table cache is used to improve the performance for full table scan\.

 

6\.Full Database caching:

 

Caching the entire database provides significant performance benefits, especially for workloads that were previously limited by I/O throughput or response time\. More specifically, this feature improves the performance of full table scans by forcing all tables to be cached\. This is a change from the default behavior in which larger tables are not kept in the buffer cache for full table scans