Disk I/O Instructions

DISK I/O Instructions

Through disk input/output instructions, information or data is stored and retrieved as logical records within files on the disk. Though PL/B files default to 256-byte sectors, the sector size may be modified by using the BUFFER or FIX{ED} parameters when they are declared in the User Data Area (UDA). PL/B records may span more than one sector and a sector may contain more than one record. Refer to the File Definition section for more information on declaring an appropriate sector size through usage of the BUFFER or FIX{ED} parameters.

The Sunbelt runtimes support 64 bit file I/O. This allows processing of files larger than 4GB by the PL/B disk I/O language statements within the operating system limits. Windows 98/ME only supports files of 2GB or smaller.

The following topics relate to Disk I/O:

File Structures	Overview of disk file structures.
File Access Methods	Overview of disk file record structures.
File Accessing Modes	Overview of disk file accessing methods.
File and Record Locking	An explanation of the file and record locking techniques.
Character String Variables	Discussion of character string handling in Disk I/O instructions.
Numeric Variables	Discussion of numeric variable handling in Disk I/O instructions.
Partial I/O	Overview of Partial I/O in Disk I/O instructions.
End of File and End of Record Marks	Definition of the End of File and End of Record marks.
List Controls	Explanation of List Controls used in Disk I/O.
RMSRAS Support	An explanation of the RMS Remote Access Server support.
Managed File Support	An explanation of the Data Manager and Managed File support.
Simplified File IO	An description of Sunbelt's simplified disk IO support.
Transactions	An description of Sunbelt's transaction support.
Version 8.7 File Format Support	An description of version 8.7 file format support.
IO using SQLite	A guide to name-based IO.
SQLITE Date/Time Tips	Tips to using the SQLITE Date and Time functions in your program.
Windows Drive Substitution	An explanation of the drive letter substition mechanism.
IO READ Cancellation	An explanation of the READ cancellation mechanism.

BTRIEVE	Execute a BTRIEVE function.
CLOSE	Close a disk file.
COUNTKEYS	Retrieve the number of keys in an ISAM file between a starting and ending value inclusively.
DELETE	Delete a record from a disk file.
DELETED	Delete a duplicate record from an ISAM disk file.
DELETEDK	Delete a duplicate ISAM key.
DELETEK	Delete an ISAM key.
ERASE	Delete a file from disk.
FILEIO	Perform file I/O functions on a file.
FILEPI	Lock specified files.
FILTER	Filter records.
FINDDIR	Retrieves file and directory names.
FINDFILE	Locates and retrieves statistical data about a file.
FLUSH	Force directory information to disk.
FLUSHEOF	Compatibility instruction - no action performed.
FPOSIT	Retrieve the current position of the file pointer.
FPOSITA	Retrieve the current position of the AAM file index.
FPOSITB	Retrieve the beginning position of the current record.
FPOSITC	Retrieve the record position following the last byte accessed.
GETFILE	Retrieve information from a file definition variable.
GETFNAME	Invoke the standard file open or prep dialog.
INSERT	Insert a key into an AAM or ISAM file.
OPEN	Initialize a disk file for access.
POSITEOF	Position the file pointer to the end of file.
PREPARE	Create or open a disk file.
PREPDEFAULT	Setup default strings for a standard file prep dialog.
READ, READTAB, READLK	Retrieve information from disk into variables.
READKEY	Return the key associated with the last indexed record accessed.
READKG, READKGTB, READKGLK	Retrieve subsequent key matching records from an AAM file.
READKGP, READKGPLK	Re-read AAM file records in reverse order.
READKP, READKPTB, READKPLK	Read ISAM files in descending (reverse) key sequence order.
READKS, READKSTB, READKSLK	Read ISAM file in ascending (forward) key sequence order.
READLAST, READLASTLK	Read the last matching record of an AAM file.
RENAME	Change the name of a disk file.
REPOSIT	Reposition the file pointer to a specified value.
SCHEMA	Execute operations specialized to the runtime schema support.
SETFILE	Updates information in a file definition variable.
STREAM	Input or output data using file redirection.
TRANSACTION	Group file IO operations.
UNLOCK	Unlock all specified files.
UPDATE, UPDATAB	Partially or completely update an ISAM or AAM record.
WEOF	Establish the end of file at the position indicated.
WRITAB	Write data to a specific location in a sector.
WRITE	Transfer variables to a disk file.