DITTO command ---- Allocate a DITTO device
Allocates a DITTO input/output device. The device may be a magnetic tape or a disk file.
DITTO allows single or multiple disk files to be allocated to the input/output device. A single disk file is denoted by specifying the full disk file name. Multiple disk files are denoted by a file name appended with "_x" and then the extension (e.g. NY_x.IMG), where x is an ascending file number.
- DEVTYPE
- Device type. Specifies which input/output device is to be allocated. Valid values are:
= INPUT : Input device = OUTPUT: Output device
- INFILE
- Input file. File name of the disk file that is to be allocated to the DITTO input/output device.
- RECTYPE(--)
- Record type. Specifies the type of records the file contains. If the file consists of variable length records, it is assumed that the file is not blocked, i.e., logical record size is equal to physical record size. Valid values are:
= --: Defaults to whatever current file is = FIX: Fixed length logical records = VAR: Variable length logical records
- RECSIZ(--)
- Record size. The number of bytes in one logical record. If the file consists of variable length records, the parameter RECSIZ represents the maximum record size within the file. The default value depends on parameter DEVTYPE:
DEVTYPE = INPUT -- RECSIZ is assigned to the logical record size of the existing disk file. DEVTYPE = OUTPUT-- RECSIZ is assigned to be a no value. Then when a DITTO command (such as COPY) is executed, the logical record size from the input device is assigned.
- BLKSIZ(--)
- Block size. The number of bytes in one physical record. Each physical record may contain more than one logical record. The use of blocked records serves to utilize as much tape and/or disk as possible and also to minimize access time. The default value depends on parameter DEVTYPE:
DEVTYPE = INPUT -- BLKSIZ is assigned to the block size of the existing disk file. DEVTYPE = OUTPUT -- BLKSIZ is assigned to be a no value. Then when a DITTO command (such as COPY) is executed, the block size from the input device is assigned.
- CCFORM(--)
- Carriage control format. The default allows the operating system to determine what type of carriage control is associated with the file. On VMS systems, this parameter may be ignored. However, UNIX systems may not be able to determine the type of carriage control correctly. Valid values are:
=--: Defaults to whatever current file is =CARRIAGE: Records terminated by a new line character =NONE: Records terminated as specified by record size
- DEVTYPE
- Device type. Specifies which input/output device is to be allocated. Valid values are:
= INPUT : Input device = OUTPUT: Output device
- COMMENT
- Description of tape. A text string sent to the operator's terminal. COMMENT consists of two pieces of information:
1. Tape library storage location ID number 2. Short description of the tapeThe operator uses this text to find the tape to be mounted; therefore, COMMENT should be as descriptive as possible. Including both the ID number and a short description gives the operator a double check to ensure the correct tape gets mounted.
- TAPEDENS(&$TPDENS)
- Tape density. The density of the tape in bytes per inch. Note that on input, the density defaults to the value of the tape being read.
- RECTYPE(--)
- Record type. Specifies the type of records the file contains. If the file consists of variable length records, it is assumed that the file is not blocked, i.e., logical record size is equal to physical record size. Valid values are:
= --: Defaults to whatever current file is = FIX: Fixed length logical records = VAR: Variable length logical records
- RECSIZ(--)
- Record size. The number of bytes in one logical record. If the file consists of variable length records, the parameter RECSIZ represents the maximum record size within the file. The default value depends on parameter DEVTYPE:
DEVTYPE = INPUT -- RECSIZ is assigned to the logical record size of the existing disk file. DEVTYPE = OUTPUT-- RECSIZ is assigned to be a no value. Then when a DITTO command (such as COPY) is executed, the logical record size from the input device is assigned.
- BLKSIZ(--)
- Block size. The number of bytes in one physical record. Each physical record may contain more than one logical record. The use of blocked records serves to utilize as much tape and/or disk as possible and also to minimize access time. The default value depends on parameter DEVTYPE:
DEVTYPE = INPUT -- BLKSIZ is assigned to the block size of the existing disk file. DEVTYPE = OUTPUT -- BLKSIZ is assigned to be a no value. Then when a DITTO command (such as COPY) is executed, the block size from the input device is assigned.
- CCFORM(--)
- Carriage control format. The default allows the operating system to determine what type of carriage control is associated with the file. On VMS systems, this parameter may be ignored. However, UNIX systems may not be able to determine the type of carriage control correctly. Valid values are:
=--: Defaults to whatever current file is =CARRIAGE: Records terminated by a new line character =NONE: Records terminated as specified by record size
- DRIVE(--)
- Tape drive. The drive that has already been selected.
- LENGTH(--)
- Tape length. The length of a tape on a drive that has already been selected. This parameter is ignored if DRIVE is NULL.
The user has requested to allocate the input DITTO device to the disk file "NY.DAT." If the file "NY.DAT" exists on disk, the single file is allocated. If "NY.DAT" does not exist and "NY_1.DAT" does exist, all disk files with the format "NY_x.DAT" are allocated to the input device. The block size and record size are assigned to whatever the existing file is.
The user has requested to allocate the output DITTO device to the disk file "NY.DAT" with a block size of 512 bytes and fixed length record size of 80 bytes.
The user has requested to allocate the output DITTO device to the disk file "NY.DAT" with variable length records with a maximum length of 100 bytes. Note that the block size is also assigned a value of 100 bytes.
The user has requested to allocate the input DITTO device to the tape identified by M0055. The tape is mounted onto a tape drive. The record size and block size are assigned to whatever the current file on tape is.
From the input parameters it is determined which input/output DITTO device is to be allocated and whether the device is to be assigned to a disk file or a magnetic tape.DITTO allows single or multiple disk files to be allocated to the input/output device. A single disk file is denoted by specifying the full disk file name. Multiple disk files are denoted by a file name appended with "_x" and then the extension (e.g. NY_x.IMG), where x is an ascending file number. The DITTO device is allocated with one of the following methods.
1. Disk file assigned to input DITTO device: Error checking is done to ensure the disk file exists and has the correct file attributes. The global variables for the input device are assigned appropriately. 2. Disk file assigned to output DITTO device: The global variables for the output device are assigned appropriately. 3. Tape assigned to input DITTO device: The input tape identified by the tape label is mounted onto a tape drive. The global variables for the input device are assigned appropriately. 4. Tape assigned to output DITTO device: The output tape identified by the tape label is mounted onto a tape drive. The global variables for the output device are assigned appropriately.