Columnar Flash Caching

9.6.4 Columnar Flash Caching

Oracle Exadata System Software release 12.1.2.1.0 can efficiently support mixed workloads, delivering optimal performance for both OLTP and analytics. This is possible due to the dual format architecture of Exadata Smart Flash Cache that enables the data to be stored in hybrid columnar for transactional processing and also stored in pure columnar, which is optimized for analytical processing.

In addition, Exadata Hybrid Columnar Compression balances the needs of OLTP and analytic workloads. Exadata Hybrid Columnar Compression enables the highest levels of data compression and provides tremendous cost-savings and performance improvements due to reduced I/O, especially for analytic workloads.

In Oracle Exadata System Software release 12.1.2.1.0, Exadata Smart Flash Cache software transforms hybrid columnar compressed data into pure columnar during flash cache population for optimal analytics processing. Flash caches on pure columnar data in flash run faster because they read only the selected columns, reducing flash I/Os and storage server CPU consumption.

Oracle Exadata System Software release 12.1.2.1.0 has the ability to cache Exadata Hybrid Columnar Compression table data on flash cache in a pure columnar layout. When Exadata Hybrid Columnar Compression tables are accessed using Smart Scan, the Exadata Hybrid Columnar Compression compressed data is reformatted to a pure columnar layout in the same amount of storage space on flash cache.

The percentage of data for a given column in a compression unit (CU) for a wide table is small compared to narrow table. This results in more CUs being fetched from disks and flash to get data for the entire column. Queries reading only a few columns of a wide Exadata Hybrid Columnar Compression table exhibit high I/O bandwidth utilization due to irrelevant columns being read from storage. Storing the data in a columnar format on flash cache alleviates the need for reading the irrelevant columns and provides a significant performance boost.

Depending on the type of workload (OLTP or data warehousing), the same region of data can be cached in both the traditional block format as well as the columnar format in flash cache.

This feature is enabled by default; you do not need to configure anything to use this feature.

Columnar Flash Caching accelerates reporting and analytic queries while maintaining excellent performance for OLTP style single row lookups.

Columnar Flash Caching implements a dual format architecture in Oracle Exadata Database Machine flash by automatically transforming frequently scanned Exadata Hybrid Columnar Compression compressed data into a pure columnar format as it is loaded into the flash cache. Smart Scans operating on pure columnar data in flash run faster because they read only the selected columns reducing flash I/Os and storage server CPU.

The original Exadata Hybrid Columnar Compression formatted data can also be cached in the flash cache if there are frequent OLTP lookups for the data. Therefore the Exadata Smart Flash Cache automatically optimizes the format of the cached data to accelerate all types of frequent operations.

This feature is enabled by default; you do not need to configure anything to use this feature.

Minimum software: Oracle Exadata System Software release 12.1.2.1.0 running Oracle Database 12c release 12.1.0.2.0.