Index for Section 3

Alphabetical listing for R

Bottom of page

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 (recno) 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_long flags;
	       u_int cachesize;
	       u_int psize;
	       int lorder;
	       size_t reclen;
	       u_char bval;
	       char *bfname;
       } RECNOINFO;

  The elements of this structure are defined as follows:

  flags
      The flag value is specified by ORing 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. Any
	      records, inserted into the database, that are less than reclen
	      bytes long are automatically padded.

      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.

  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 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.

  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.

  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.

  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.

  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 size of that type.

  Because there can be no metadata associated with the underlying recno
  access method files, any changes made to the default values (for example,
  fixed record length or byte separator value) must be explicitly specified
  each time the file is opened.

  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.

RESTRICTIONS
  Only big and little endian byte order is supported.

ERRORS
  The recno access method routines may fail and set errno for any of the
  errors specified for the library routine dbopen(3) or the following:

  [EINVAL]
      An attempt was made to add a record to a fixed-length database that was
      too large to fit.

SEE ALSO
  btree(3), dbopen(3), hash(3), mpool(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.

Index for Section 3

Alphabetical listing for R

Top of page