Tivoli Header

Tivoli Storage Manager Using the Application Program Interface

Compression

The end user's configuration, along with the dsmSendObj objCompressed flag, determines whether TSM will compress the object during a send. Also, objects with a sizeEstimate less than DSM_MIN_COMPRESS_SIZE will never be compressed.

If the object is compressed already (objCompressed=bTrue), it is not compressed again. If it is not compressed, TSM decides whether to compress the object, based on the values of the compression option that is set by the TSM administrator and is set in the API configuration sources.

The TSM server administrator can affect compression behavior with the register node command (compression=yes, compression=no, or client-determined). If this is client-determined, then the compression behavior is determined by the option value in the configuration sources.

Some types of data, such as data that is already compressed, might actually get bigger when processed with the compression algorithm. When this happens, the return code DSM_RC_COMPRESS_GREW is generated. If you realize that this might happen, but you want the send operation to continue anyway, tell the end users to specify the following option in their options file:

   COMPRESSAlways Yes

Attention: If your application plans to use partial object restore or retrieve, you cannot compress the data while sending it. To enforce this, set ObjAttr.objCompressed to bTrue.


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