RECNO(3)						     Linux Programmer's Manual							  RECNO(3)

NAME

       recno - record number database access method

SYNOPSIS

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

DESCRIPTION

       The  routine  dbopen(3) 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(3) is defined in the <db.h> include file as follows:

	   typedef struct {
	       unsigned long flags;
	       unsigned int  cachesize;
	       unsigned int  psize;
	       int	     lorder;
	       size_t	     reclen;
	       unsigned char bval;
	       char	    *bfname;
	   } RECNOINFO;

       The elements of this structure are defined as follows:

       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.  Any records, inserted into the database,  that  are	less  than  reclen
		     bytes long are automatically padded.

	      R_NOKEY
		     In  the interface specified by dbopen(3), 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  applica-
		     tions 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(3) 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 mem-
	      ory 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 ("
") 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 filename for a dbopen(3) 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 th <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 (e.g.,
       fixed record length or byte separator value) must be explicitly specified each time the file is opened.

       In the interface specified by dbopen(3), 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.

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.

BUGS

       Only big and little endian byte order is supported.

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, Mem-
       orandum No. UCB/ERL M82/32, May 1982.

COLOPHON

       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

4.4 Berkeley Distribution					    1994-08-18								  RECNO(3)