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# Modify server configuration symbols

You can optimize performance by modifying parameters in the dm.cfg configuration file on the Dimensions CM server.

In this topic:

## Considerations

When making network changes, consider what impact the change may have on other applications using the network and the server.

- Each Dimensions CM server or client installation contains a dm.cfg file located in the %DM_ROOT% (Windows) or $DM_ROOT (UNIX) directory. If the installation is part of a larger network of Dimensions CM installations, check that configuration settings affecting communication with other installations are the same for all installations.

- Settings in the dm.cfg file are installation-wide. Parameters that are specific to you must be set in your environment. If settings are made in the dm.cfg configuration file and in your environment, your environment takes precedence.

- The configuration parameters and environment variables are generically referred to as Dimensions CM symbols. Most Dimensions CM symbols are supported on all the operating systems.

- Some symbols require the Dimensions CM listener to be stopped and started before the change takes effect.

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## Modify configuration symbols

1. Navigate to the dm.cfg configuration file. Default locations:

   Windows | %DM_ROOT%\dm.cfg
   UNIX | $DM_ROOT/dm.cfg

2. Make a copy of dm.cfg.

3. Open dm.cfg.

4. Modify, add, or remove symbols.

5. Save and close the file.

6. Restart the Dimensions CM listener.

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## Configuration symbol reference

The following table describes the configuration symbols in dm.cfg that you can modify to improve performance:

Symbol | Description
--- | ---
`DM_SOCKET_OPTIONS` | The values of the options for this parameter can be customized to optimize network throughput. Use the following option values to configure the TCP/IP send and receive buffers: `SO_RCVBUF(bdp value)` `SO_SNDBUF(bdp value)` where bdp (bytes) is set to the bandwidth-delay product (BDP). See Optimize performance based on bandwidth. The TCP_NODELAY option controls the turning off or on the delayed acknowledgments (ACKs). See Disable ACKs and the Nagle algorithm. Example: `DM_SOCKET_OPTIONS TCP_NODELAY(1),SO_LINGER(1,5),SO_REUSEADDR(1),SO_KEEP ALIVE(1),SO_RCVBUF(125000),SO_SNDBUF(125000)`
`DM_NETWORK_BLOCKSIZE` | Set to 1000 bytes or more but not exceeding the value of BDP. Makes room for the Dimensions CM message headers. File blocksize must not exceed the network blocksize.
`DM_FILE_BLOCKSIZE` | Set to 4000 bytes or more but not exceeding the value of DM_NETWORK_BLOCKSIZE. Makes room for the Dimensions CM message headers.
`DM_FILECACHE_SIZE n` | All files that are not library cached go through the memory file cache. When the cache is full, the files stored in the cache are sent to the client. The memory file cache buffers data up to a maximum size. n is equal to one of these values: Default value: 4194304B (4 MB) The following value may improve performance: 8388608B (8 MB) See Memory file cache.
`DM_COMPRESSION_MIN_FILELENGTH` | Dimensions CM supports stream compression on file transfer using ZLIB. Specify a compression threshold. Files smaller than the threshold value are not considered for compression. The default minimum file size for compression is 2K. See Optimize the file compression levels‌.
`DM_COMPRESS_FILES_ON_TRANSFER` | Enables file compression to speed up file transfers.
`DM_DONT_PREFETCH_FROM_LIBRARY` | Improves performance when getting files from a Dimensions CM server on AIX. Add this symbol and set it to y: `DM_DONT_PREFETCH_FROM_LIBRARY y`
`DM_RANDOMIZE_LIBRARY_PATHS y` | The server automatically spreads new files mapped to the same item type across X/Y/ subfolders of the corresponding item library folder, where X and Y are the first two hex digits from a cryptographically secure checksum hash of the corresponding item library path name.

For a complete list of Dimensions CM server and client symbols, see Administration.

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See also:

- Optimize Dimensions CM

https://admhelp.microfocus.com Dimensions CM 8942
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