The OPEN statement defines the characteristics of the magnetic tape files that are used in a process. The statement is used to assign blocking factors, record lengths, record formats, label formats, conversion information on' either input or output data files, and positioning to records or files.
The format for the OPEN statement is: remaining parameters may be input in any order.
• Inn-input
!
indicates that the OPEN statement applies to the input device, where nn specifies the one- or two-digit logical number of the input device. If nn is omitted, the standard input logical unit number is assumed. number is assumed.• VFnn-verify
VF indicates that the OPEN statement applies to the verify file, where nn specifies the one- or two-digit logical unit number of that file. If nn is omitted, the standard output logical unit number is assumed. .
o PRnn-print
PR indicates that the OPEN statement applies to the list device, where nn specifies the one- or two-digit logical number of that device. If nn is omitted, the standard list device is assumed.
LABEL TYPES
• "NL
This indicates no labels, meaning perform no label processing.
Definition of the label types are as follows:
• SL-standard
Input label processing involves the verification of the volume, header, and trailer labels. Output multi-volume output processing is included in standard label processing. Labels may be American National Standard labels or EBCDIC standard labels (see conversion option on page F-2). Input label processing requires HDR1, EOF1, or EOV1 labels. Output processing generates HDR1, HDR2, EOF1, EOF2, EOV1, and EOV2labels.
If open processing of the HDR2 label is featured, it eliminates the need for specifying block size, record size, or record formats in the OPEN statement.
The discussion on page F -17 contains a complete description of label processing and label content.
• BL-bypass labels
If BL is specified the tape is positioned to the first record of the specified file. No attempt is made to
• y-variable-Iength records
In the first 32 bits of a record, 16 bits must con-tain a binary number specifying the record length.
The last 16 bits must be zero-filled.
• VB-variable-length, blocked records
In the first 32 bits of a block, 16 bits must contain
a binary number which specifies the block length . The next 16 bits must be zero-filled. The frrst variable-length record of the block must follow the 32 bits.
• E-fixed-Iength records
Each record must be exactly the same length.
• FB-fixed-Iength, blocked records
Each block must contain an integral number of fixed-length records. There is no requirement that the block length remain fixed. Fixed blocking usually has a maximum length.
• V-undefined record format
Each record is treated as an undefined, variable-length record. Blocking cannot be used in the undefined format. Print files may be specified as
1!
only. If the format parameter is omitted, V is assumed. Refer to page F-23 for a description of each record format.DATA FORMAT
The following parameters specify data conversion. To specify conversion, both the input and output file data formats must be defined. For example, if the input data format is specified as
A
(ASCII) and the output tape is specified asg
(EBCDIC) the conversion of ASCII to EBCDIC takes place. If the data format of the specified input and output files is the same or not given, no conversion takes place.• B
B indicates the specified tape file contains BCD data (seven-track only).
• E
E specifies the tape file contains EBCDIC data. If SL is specified, E implies EBCDIC labels are to be read or written. standard, E causes System/360/370, OS/DOS/VS-compatible labels to be generated.
The data format code may be necessary to list or dump certain data tapes since the system printer can accept only one data format. If the file is to be properly printed, therefore, the conversion code must be specified. Binary data does not require conversion. The default is either binary or ASCII. Refer to the conversion tables on page F-24.
POSITIONING AND SELECTIVE RECORD PROCESSING
Parameters, which cause input or output files to be positioned to a given record and file, may be specified.
Other parameters may be specified to selectively process records used as input to or output of the COS assembler.
These parameters are:
o SFnn-skip files
This parameter specifies skip nn files before processing where nn is a one- or two-digit decimal number. Skip files may be used on either input or output files.
o BRnnnnn-bypass records
This parameter specifies bypass nnnnn records before processing where nnnnn is a with the parameters PNAM, TNAM, SNAM, or NAM because the result-ing output is unreliable.
o PNAM (='XXXXXX'}-position to name This parameter specifies positioning of a data file to a name statement or name block which con-tains the name specified by XXXXXX where XXXXXX is a one-to-six-character name. If XXXXXX is not specified, the first NAM block or statement is used. The PNAM parameter bypasses all records prior to the specification condition. Positioning of files occurs during an operational function; therefore, the input file is not positioned during OPEN processing.
SELECTIVE PROCESSING OF PARAMETERS Selective processing which uses the SNAM, TNAM, and NAM parameters specifies positioning to given records
as in PNAM and termination of the process when the record is found. Selective processing can occur only on input files. Processing files that are not 1700 source data, listable, or relocatable records produce unreliable results. Selective processing does not require a specified type of file (source listable or relocatable).
o TNAM (='XXXXXX'}-terminate name
This indicates the termination of processing on the specified name statement or block. If XXXXXX is specified, termination occurs when the name specified by XXXXXX is located. If XXXXXX is not specified, the file is terminated on the first name statement or block. Where TNAM and PNAM are used jointly, termination tests are not executed until at least one record has been processed. This feature allows the processing of all records between specified name statements and blocks.
o SNAM (='XXXXXX'}-select name and terminate
This specifies the selection of records following and including the specified name statement or block and terminates processing on the next name statement or block. SNAM is similar to using the PNAM and TNAM parameters where PNAM specifies the name block and TNAM does not specify a particular name block. SNAM may be used, therefore, to selectively process one file delimited by name statements.
o NAM (='XXXXXX'}-name blocks associated input file.
SPECIFICATION OF RECORD SIZES
Before processing a data file, the block size and/ or maximum values; however, if fixed-length records or blocks are specified, the record size must be the exact F-S
record size. If record and block sizes are incorrectly specified, a warning message is used to indicate the error.
Processing is possible if a warning occurs; however, results are unpredictable.
Since records are read and written from allocated storage, it is possible that excessive block or record sizes could exceed the available storage. The OPEN statement precludes this possibility by terminating and issuing a severe error message, indicating insufficient storage. (see page F-14). The following parameters may be used to specify associated block and record sizes.
• LBnnnnn-length of block
This indicates the maximum block length where nnnnn is a one-to-five-digit decimal number (not greater than 32,767), specifying the number of
• LRnnnnn-length of record
This indicates the maximum record length where nnnnn is a one-to-five-digit decimal number (not greater than 32,767) specifying the maximum number of characters in a record. If fixed block is specified, LR is the exact length of each record.
For PR files, LR is used as the form's width.
• LCnnnnn-line count per page
This specifies the number of lines per page before ejecting the page (only valid for PR files). If LC is unspecified, S6 lines per page is assumed. By specifying zero, line counting is inhibited.
NOTE
Because of operating restrictions, block and record sizes must be a multiple of two characters.