In this topic will be discussed with Exadata Key Features
- Smart Scan or Cell Offloading
- Storage Indexes
- Hybrid Columnar Compression
- IO Resource Manager
- Smart Flash Cache
- Flash Logging
Smart Scan or Cell Offloading:
Smart Scan is one of the great feature in Oracle Exadata. With this technology storage send only required byte to database node from storage instead of entire Oracle Block. Multiple rows are stored in one Oracle Block but non-exadata system return entire block even only one rows is required. On the other hand, Exadata Storage returns only interested bytes not entire block.
Details about Smart Scan or Cell Offloading
A storage index is a memory-based structure that reduces the amount of physical I/O performed in an Exadata cell. The storage index keeps track of minimum and maximum column values and this information us used to avoid useless I/Os.
Exadata Hybrid Columnar Compression:
- Oracle introduced basic compress feature from Oracle 9i version.
- Exadata Hybrid Columnar Compression can be specified at Table or Table Partition and Tablespace Level.
- Not Suitable for data which is frequently changing.
- Locking at CU level instead of row level so potentially many rows could be locked instead of single row
- Data needs to be loaded using direct path loads like Parallel DML, INSERT /*+ APPEND*/, direct path SQL Loader
Details about Hybrid Columnar Compression
Smart Flash Cache:
- Oracle Exadata Smart Flash Cache stores frequently access data in Flash Storage which is very fast than other storage. This happens automatically and user don’t need to take any action to use this feature.
- Flash Cache is Smart – it avoids caching data which will not be reused or which is too big to fit in cache.
- The Exadata Storage Server Software also provides the Exadata Smart Flash Logging feature to speed database log I/O