Hybrid Columnar Compression (HCC) is an advanced storage compression technology introduced in Oracle Database 11g. HCC is designed to reduce storage requirements and improve query performance for large-scale data warehouses and archival systems. HCC achieves this efficiency by storing data in columns instead of rows and compressing similar data values together.
Here are some best practices for implementing HCC in Oracle databases:
1. Choose the Right HCC Format: Oracle offers three compressions algorithms: Query Low (QL), Query High (QH), and Archive High (AH). QL compression is best suited for read-mostly systems, QH is well-suited for OLTP systems with high write activity, and AH is ideal for archival data where quick retrieval is not a priority.
2. Define Appropriate Data Segmentation: It is essential to segment data based on access frequency to maximize storage efficiency. Frequently accessed data should not be compressed due to the overhead of decompression during query processing. Segmentation is also necessary to set compression parameters such as block size and column order.
3. Combine HCC with Partitioning: HCC is especially useful when combined with partitioning. The partitioning of data can be based on any criterion, such as time, region, or department, resulting in more efficient compression.
4. Monitor Compression Ratios: As HCC compression is based on the similarities between data values, it is essential to monitor compression ratios. A low compression ratio implies that there is little redundancy in the data, and HCC may not be optimal for that dataset.
5. Utilize HCC with Exadata: HCC is particularly efficient when used with Exadata, Oracle’s specialized hardware designed to work with its database software. This combination can reduce storage requirements and query processing times.
The impact of HCC on storage efficiency and query performance is significant. HCC can reduce storage requirements by 10x to 50x and improve query performance by 3x to 4x. In some cases, depending on the data and workload, customers have achieved up to 70
In conclusion, to achieve the best results with HCC, it is essential to choose the right compression format, segment data effectively, combine it with partitioning, monitor compression ratios, and use it with specialized hardware like Exadata. HCC can offer incredible storage efficiency and query performance gains for large-scale data warehouses and archival systems.