The catalogues in DIRA2 are identified by logical names of 12 or less characters; the name do not contains special symbols and are uppercase. When possible, the name coincides with that used by the astronomical community (AGK3, SAO, MCG); in many cases, however, we had to redefine abbreviations and codes. We also tried to refer to standard already in use (e.g., ADC or CDS acronym Kempt 1960, Dixon 1976 etc.). Knowledge of the name of the catalogue is needed to access data.
When the identification name of a catalogue is not known, the user can use the DB_INFO command to search by keys (author, title, subject, band, ADC or CDS identification) among the available catalogues.
The catalogues can be used on disk or on tapes in the same way, but working with data on tapes is very slow. Therefore a structure of virtual disk has been defined. If there is enough free space on disk and a scratch area is available to the user, the Data Base Administrator can decide that the catalogues are copied on disk before their use. When a catalogue is required, it is automatically copied on disk and is available to everyone. By entering the command DB_INFO, it is possible to check if the catalogues in a computer center are on disk, or on tape.