The nucleotide sequence database collected and maintained by DDBJ is quarterly released on line to the public and distributed in the magnetic media.We completed DDBJ Release 37 in Mar. 26, 1999. DDBJ Release 37 consists of 3,311
,627 entries,and the number of bases reached 2,375,261,951.
Since the content of a nucleotide sequence is often revised due to replacements,additions and deletions of bases made by the submitter,the accession number sometimes does not work to tell which sequence is really in question.Thus, an additional identifier was introduced to specify a particular sequence in a series of revised sequences.This identifier is called NID. For the same reason for translated amino acid sequences, PID was brought into being.