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retrieve                                                        action
  class=od
  stream   = oper,                                  identification of archive
  expver   = 1,
  date     = -1,                                      date and time related
  type     = analysis,
  levtype  = model levels,
  levelist = 1/to/91,
  param    = temperature,
  grid     = 2.5/2.5,                           post-processing
  area     = europe,
  use      = infrequent,                    execution control
  target   = analysis.12                    storage

Retrieve requests have to specify, at least, directives to identify the data and directives for storage of the retrieved data. The ones to identify fields can be found in the Archive Catalogue. Data manipulation (post-processing) directives and execution control directives are optional, depending on user's needs.

With the main focus on data retrievals, this User Guide covers the following MARS actions, or verbs:

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write is mainly used to save data from fieldsets, a temporary storage, into files, see section 5.2.

Fieldsets

A fieldset is a temporary storage for fields, either retrieved from MARS or read from a UNIX file. Fieldsets can be seen as variables in a MARS request, and they can be referenced in subsequent MARS requests in the same execution. This is an example how to retrieve data into a fieldset named analysis:

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The advantage of retrieve is that it will fail if the requested data is not present in the source file. A disadvantage is that it has to specify all the directives, and the user might not know what are the exact contents of the source file.date     = -1,