The directory server provides two mechanisms for reducing the size of stored data:
Compact encoding. When compact encoding is enabled, the back end uses a compact form when encoding entries by compressing the attribute descriptions and object class sets. This property applies only to the entries themselves and does not impact the index data. Compact encoding is enabled by default but can be disabled if required. You might want to disable compact encoding where user-supplied capitalization is required because user-supplied capitalization is not preserved in compacted entries. The compaction does, however, provide a performance gain and is therefore beneficial in deployments where user-supplied capitalization can be sacrificed for performance, or is not required.
Entry compression. Entry compression uses a deflater to compress the data before it is stored. When entry compression is enabled, the back end attempts to compress entries before storing them in the database. This property also applies only to the entries themselves and does not impact the index data. The effectiveness of entry compression is based on the type of data contained in the entry.
You can enable one or both of these mechanisms to reduce the size of the stored data. Because enabling these mechanisms affects future writes only, the database might contain a mixture of compressed and uncompressed records. Either type of record can be read regardless of the compression settings.