Data in an Xtal archive file is separated into blocks referred to as logical records. The names of these records lrhist:, lrrefl:, lratom:, etc. indicate the nature of the data stored therein. The length of a logical record varies depending to the type of data it holds, the nature of crystal structure being processed, and the current state of the crystallographic analysis. A logical record is subdivided into a sequence of packets, each representing a logical subset of the data. Data for a reflection measurement, or an atom site, are typical record packets. There are two types of records: fixed format (F) and directory (D) in which the first packet contains the ID numbers of data values that follow.
The system names for logical records are lr<name>:. However, in the text archive files (.aaa or .arc) the logical records are identified by the data names starting with <name>_.
| logical record | number | Type | Contents |
| lrhist: | 1 | F | compound ID and calculation history |
| lrlabl: | 2 | F | title and labels inserted by the user |
| lrcell: | 4 | F | cell and cell transformation data |
| lrsymm: | 5 | F | space group symmetry data |
| lrsgnm: | 6 | F | space group symbols and names |
| ltrwin: | 7 | F | twin laws |
| lrscat: | 8 | D | scattering factor, atom type information |
| lrsequ: | 9 | F | residue sequence information |
| lrddef: | 10 | F | dataset name strings |
| lrexpl: | 11 | D | experimental parameters per dataset |
| lrdset: | 12 | D | general parameters per dataset |
| lrdict: | 13 | D | macromolecular residue information |
| lrgraf: | 14 | D | molecule orientation information |
| lratom: | 16 | D | atom site parameters |
| lrcons: | 17 | D | atom constraints information |
| lrslav: | 18 | F | macromolecular atom link information |
| lrmole: | 19 | D | molecular formula and cell content data |
| lrrefl: | 20 | D | reflection data |
| lrthet: | 21 | F | precise angle data for cell dimensions |
| lrsfls: | 30 | D | sfls refinement results |
| lrrfac: | 31 | F | sfls R-factor refinement history |
| lrdens: | 35 | D | electron density data |
| lrbond: | 40 | D | bond distances |
| lrcont: | 41 | D | contact distances |
| lrangl: | 42 | D | bond angles |
| lrdihe: | 43 | D | dihedral angles |
| lrrigi: | 44 | D | rigid link constraints |
| endrecord: | 65535 | F | terminal archive record |
Only the contents of archive files are described here. Information about the contents of auxiliary binary data files must be obtained from the source file of the generating program.
Each logical record is listed as:
A header line containing:
the default logical record type number,
the logical record name,
the logical record format (F for fixed format; D for directory access ) and
a synopsis of the information stored.
A second line with the packet size information.
For fixed format records, the column headed SEQ gives the packet indices for items listed. For directory records, the column headed IDN gives the identification (ID) numbers of the items that may appear in the logical record. Remember that these are the numbers which are stored in the first packet of a directory record.