Concepts: WOS and ROS

Concepts: WOS and ROS:

What is WOS:

Write Optimized Store (WOS) is a memory-resident data structure for storing data loaded (or removed) using the INSERT, UPDATE, DELETE, and COPY statements, without /*+direct*/ hints.

Like the Read Optimized Store (ROS), the WOS is arranged by projection.

To support very fast data load speeds, the WOS stores records without data compression or indexing.

A projection in the WOS is sorted only when it is queried. It remains sorted as long as no further data is inserted into it. The WOS organizes data by epoch and holds both committed and uncommitted transaction data.

What is ROS:

The Read Optimized Store (ROS) is a highly optimized, read-oriented, disk storage structure, organized by projection.

The ROS makes heavy use of compression and indexing.

You can use the COPY statement DIRECT and INSERTparameters (with /*+direct*/ hint) to load data directly into the ROS.