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# NodeTableCompression

When you configure the `NodeTableCompression` parameter, IDOL Server compresses data in the nodetable directory before storing it, to reduce the disk footprint.

The overhead of compressing and decompressing document data might incur a performance penalty. However, on some systems that are bound by I/O rather than processor bottlenecks, the performance might be only marginally affected, or even improved, because the reduced volume of reading and writing data can largely offset the increased computational costs of the compression.

You can specify the compression algorithm to use. HPE recommends that you use `lz4` compression , which provides the best balance between performance and reduction of disk footprint over a range of data sets. However, you might want to trial multiple compression options to determine the most appropriate value for your use case. The `zlib` and `lz4hc` methods tend to reduce the data size most, but these are more computationally expensive. The `snappy` method is comparable with `lz4` in terms of performance and compression methods, but might perform better on certain data sets.

Note: Indexes that consist mainly of very short documents, such as Twitter feeds, might not compress effectively.

If you change this setting after you have indexed data, IDOL Server does not immediately recompress your index. When you run an index action that adds data or rewrites existing data (such as `DREREPLACE`), it uses the new compression method. You can also run a `DRECOMPACT` index action with the `NodeTableCompactWindowKB` parameter set to apply the new compression method to your index.

Note: You can only increase compression by using the `DRECOMPACT` index action. For example, if you change `NodeTableCompression` from `lz4` to `Off`, the compaction does not decompress your data.

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