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| Tiled Array Storage files (aka TAS files) are FITS files that comprise one or more, equally-sized data slices. Each slice is the data for a single DRMS record of a DRMS data series. | One of the segment protocols is "TAS". Under this protocol, series data are stored in Tiled Array Storage files (aka TAS files) in SUMS directories. This option exists because it allows the user to combine multiple images (or collections of data) into a single file for storage purposes. It is beneficial to do this, as this results in fewer, larger files and this improves disk-and-tape management performance. It is also a method for keeping related data together as it shuttles between disk and tape. A TAS file comprises one or more, equally-sized data slices. Each slice is the data for a single DRMS record of a DRMS data series. In fact, TAS files are simply FITS files that contain data slices. A series creator specifies the number of slices in a TAS file by using the Unitsize field in the series' JSD. Just as the unitsize determines the maximum number of slot directories in a SUMS storage-unit directory for data with a segment protocol of FITS, for TAS segments, the unitsize determines the ''maximum'' number of data slices in a TAS file (and since a slice corresponds to a single DRMS record, it is equivalent to say that the unitsize is the maximum number of DRMS records whose data is contained by the TAS file). To create a DRMS data series with a TAS segment, you simply need to specify "tas" in the protocol field of the segment's series definition file (please see the discussion on [Jsd series definition] files for more information). You should also consider choosing appropriate <tile-compression arguments> should you decide that you want your TAS files compressed (yes, you want your TAS files compressed). This field in the JSD is a string that is passed directory to CFITSIO (remember, TAS files are FITS files) as the file-name modifier (please see the latest CFITSIO documentation). The file-name in the CFITSIO paradigm is how a user controls various aspects of compression. Please see the discussion on [Jsd series definition] files for more information about the remaining fields of the segment specification. If the protocol is tas the AND the TAS file is to be tile-compressed, TAS tile sizes must also be specified in the <tile-compression arguments> field. TAS files may also be uncompressed, in which case, there is no tiling. "compress <algorithm> <tilesize1>,<tilesize2>...<tilesizeN>" If the string is "compress" then by default the algorithm is Rice and the data are row-compressed. If the string contains tile sizes, then the size specified overrides the default row-compression. For the TAS protocol, in most cases the user should specify tile sizes and not rely upon row-compression. |
TAS Files
One of the segment protocols is "TAS". Under this protocol, series data are stored in Tiled Array Storage files (aka TAS files) in SUMS directories. This option exists because it allows the user to combine multiple images (or collections of data) into a single file for storage purposes. It is beneficial to do this, as this results in fewer, larger files and this improves disk-and-tape management performance. It is also a method for keeping related data together as it shuttles between disk and tape.
A TAS file comprises one or more, equally-sized data slices. Each slice is the data for a single DRMS record of a DRMS data series. In fact, TAS files are simply FITS files that contain data slices. A series creator specifies the number of slices in a TAS file by using the Unitsize field in the series' JSD. Just as the unitsize determines the maximum number of slot directories in a SUMS storage-unit directory for data with a segment protocol of FITS, for TAS segments, the unitsize determines the maximum number of data slices in a TAS file (and since a slice corresponds to a single DRMS record, it is equivalent to say that the unitsize is the maximum number of DRMS records whose data is contained by the TAS file).
To create a DRMS data series with a TAS segment, you simply need to specify "tas" in the protocol field of the segment's series definition file (please see the discussion on [Jsd series definition] files for more information). You should also consider choosing appropriate <tile-compression arguments> should you decide that you want your TAS files compressed (yes, you want your TAS files compressed). This field in the JSD is a string that is passed directory to CFITSIO (remember, TAS files are FITS files) as the file-name modifier (please see the latest CFITSIO documentation). The file-name in the CFITSIO paradigm is how a user controls various aspects of compression.
Please see the discussion on [Jsd series definition] files for more information about the remaining fields of the segment specification.
If the protocol is tas the AND the TAS file is to be tile-compressed, TAS tile sizes must also be specified in the <tile-compression arguments> field. TAS files may also be uncompressed, in which case, there is no tiling.
"compress <algorithm> <tilesize1>,<tilesize2>...<tilesizeN>"
If the string is "compress" then by default the algorithm is Rice and the data are row-compressed. If the string contains tile sizes, then the size specified overrides the default row-compression. For the TAS protocol, in most cases the user should specify tile sizes and not rely upon row-compression.