RECNO(3)                       1993                      RECNO(3)


NAME
       recno - record number database access method

SYNOPSIS
       #include <sys/types.h>
       #include <db.h>

DESCRIPTION
       The  routine  dbopen  is the library interface to database
       files.  One of the supported file formats is record number
       files.   The  general  description  of the database access
       methods is in dbopen(3), this manual page  describes  only
       the recno specific information.

       The  record  number  data  structure is either variable or
       fixed-length  records  stored  in  a   flat-file   format,
       accessed  by  the logical record number.  The existence of
       record number five implies the existence  of  records  one
       through four, and the deletion of record number one causes
       record number five to be renumbered to record number four,
       as  well  as the cursor, if positioned after record number
       one, to shift down one record.

       The recno access method specific data  structure  provided
       to  dbopen  is  defined  in  the  <db.h>  include  file as
       follows:

       typedef struct {
              u_char bval;
              u_int cachesize;
              index_t psize;
              u_long flags;
              int lorder;
              size_t reclen;
              char *bfname;
       } RECNOINFO;

       The elements of this structure are defined as follows:

       bval   The delimiting byte to be used to mark the end of a
              record  for  variable-length  records,  and the pad
              character for fixed-length records.  If no value is
              specified,  newlines  (``\n'') are used to mark the
              end of  variable-length  records  and  fixed-length
              records are padded with spaces.

       cachesize
              A  suggested  maximum size, in bytes, of the memory
              cache.  This value is only advisory, and the access
              method  will allocate more memory rather than fail.
              If cachesize is  0 (no size is specified) a default
              cache is used.

       psize  The recno access method stores the in-memory copies



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RECNO(3)                       1993                      RECNO(3)


              of its records in a btree.  This value is the  size
              (in  bytes)  of  the  pages  used for nodes in that
              tree.  If psize is 0 (no page size is specified)  a
              page  size  is  chosen based on the underlying file
              system I/O  block  size.   See  btree(3)  for  more
              information.

       bfname The recno access method stores the in-memory copies
              of its records in a btree.  If bfname is  non-NULL,
              it  specifies  the  name  of  the btree file, as if
              specified as the file name for a dbopen of a  btree
              file.

       flags  The  flag  value  is specified by or'ing any of the
              following values:

              R_FIXEDLEN
                     The  records  are  fixed-length,  not   byte
                     delimited.   The  structure  element  reclen
                     specifies the length of the record, and  the
                     structure  element  bval  is used as the pad
                     character.

              R_NOKEY
                     In the interface specified  by  dbopen,  the
                     sequential  record  retrieval  fills in both
                     the caller's key and  data  structures.   If
                     the  R_NOKEY  flag  is specified, the cursor
                     routines are not required to fill in the key
                     structure.   This  permits  applications  to
                     retrieve records at the end of files without
                     reading all of the intervening records.

              R_SNAPSHOT
                     This  flag  requires  that a snapshot of the
                     file be taken when dbopen is called, instead
                     of  permitting  any unmodified records to be
                     read from the original file.

       lorder The byte order for integers in the stored  database
              metadata.  The number should represent the order as
              an integer; for example, big endian order would  be
              the  number  4,321.   If  lorder  is 0 (no order is
              specified) the current host order is used.

       reclen The length of a fixed-length record.

       The data part of the  key/data  pair  used  by  the  recno
       access  method  is  the same as other access methods.  The
       key is different.  The data field of the key should  be  a
       pointer  to  a memory location of type recno_t, as defined
       in the <db.h> include file.  This  type  is  normally  the
       largest   unsigned   integral   type   available   to  the
       implementation.  The size field of the key should  be  the



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RECNO(3)                       1993                      RECNO(3)


       size of that type.

       In  the  interface  specified  by  dbopen,  using  the put
       interface to create a new record will cause  the  creation
       of  multiple,  empty  records if the record number is more
       than one greater than the largest record currently in  the
       database.

SEE ALSO
       dbopen(3), hash(3), mpool(3), recno(3)

       Document  Processing  in  a  Relational  Database  System,
       Michael  Stonebraker,  Heidi  Stettner,   Joseph   Kalash,
       Antonin  Guttman,  Nadene  Lynn,  Memorandum  No.  UCB/ERL
       M82/32, May 1982.

BUGS
       Only big and little endian byte order is supported.







































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