- Journal tables
- Join indexes
- Hash indexes
- Spool tables
- Global temporary tables
- Primary subtables
- Fallback subtables
- LOB subtables (JSON, XML, and character)
The goals of block-level compression are to save storage space and to reduce disk I/O bandwidth. Block-level compression can use significantly more CPU to compress and decompress data dynamically, so whether query performance is enhanced with block-level compression depends on whether performance is more limited by disk I/O bandwidth or CPU usage.
Teradata offers software-based and hardware-based BLC. You select the BLC method when you specify the compression algorithm in the CompressionAlgorithm field in DBS Control. See Controlling BLC at the System Level Using the DBS Control Utility.
The following site provides guidelines for evaluating the impact of block-level compression on performance and on disk space: https://downloads.teradata.com/extensibility/articles/block-level-compression-evaluation-with-the-blc-utility. The site also provides a link to download the Block Level Compression Evaluation utility.