Peter Prymmer > OS390-Stdio > stdio_cookbook

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NAME ^

stdio_cookbook - recipes and examples for the use of OS390::Stdio

DESCRIPTION ^

Examplary documentation for some of the more commonly encountered data set handling tasks is provided along with reference material that would not easily fit into the OS390::Stdio.pm pod.

NAMES and data set handles ^

To access data set names that are outside of the hierarchical file system (HFS) prepend two solidus (or forward slash) characters // to the name. If you do not use a default high level qulialifier then also enclose the fully qualified name in single quotation marks '.

For example the SYS1.PARMLIB PDS could be opened with:

    $handle = mvsopen("//'SYS1.PARMLIB'","r");
    if (defined($handle)) {
        # SYS1.PARMLIB ios open , read from $handle
    }
    else {
        warn "unable to mvsopen //'SYS1.PARMLIB'";
    }

As another example if my default HLQ is PVHP then I can mvsopen the 'PVHP.SAMPLE.SET' data set for reading and writing with the shorthand name:

    $file_handle = mvsopen("//SAMPLE.SET","w+");

mvsopen() modes ^

The second "mode" argument to mvsopen() corresponds to the mode argument to fopen() in the C programming language. From the C/C++ Run-Time Library Reference document we find the following modes:

"r"

Open a text file for reading. (The file must exist.)

"w"

Open a text file for writing. If the "w" mode is specified for a ddname that has DISP=MOD, the behavior is the same as if "a" had been specified. Otherwise, if the file already exists, its contents are destroyed.

"a"

Open a text file in append mode for writing at the end of the file. mvsopen() creates the file if it does not exist.

"r+"

Open a text file for both reading and writing. (The file must exist.)

"w+"

Open a text file for both reading and writing. If the "w+" mode is specified for a ddname that has DISP=MOD, the behavior is the same as if "a+" had been specified. Otherwise, if the file already exists, its contents are destroyed.

"a+"

Open a text file in append mode for reading or updating at the end of the file. mvsopen() creates the file if it does not exist.

"rb"

Open a binary file for reading. (The file must exist.)

"wb"

Open an empty binary file for writing. If the "wb" mode is specified for a ddname that has DISP=MOD, the behavior is the same as if "ab" had been specified. Otherwise, if the file already exists, its contents are destroyed.

"ab"

Open a binary file in append mode for writing at the end of the file. mvsopen() creates the file if it does not exist.

"rt"

Open a text file for reading. (The file must exist.)

"wt"

Open a text file for writing. If the file already exists, its contents are destroyed.

"at"

Open a text file in append mode for writing at the end of the file. mvsopen() creates the file if it does not exist.

"r+b" or "rb+"

Open a binary file for both reading and writing. (The file must exist.)

"w+b" or "wb+"

Open an empty binary file for both reading and writing. If the "w+b" (or "wb+") mode is specified for a ddname that has DISP=MOD, the behavior is the same as if "ab+" had been specified. Otherwise, if the file already exists, its contents are destroyed.

"a+b" or "ab+"

Open a binary file in append mode for writing at the end of the file. mvsopen() creates the file if it does not exist.

"r+t" or "rt+"

Open a text file for both reading and writing. (The file must exist.)

"w+t" or "wt+"

Open a text file for both reading and writing. If the file already exists, its contents are destroyed.

"a+t" or "at+"

Open a text file in append mode for writing at the end of the file. mvsopen() creates the file if it does not exist.

There are all sorts of extra things that you can tuck into the second "mode" argument to mvsopen() as well. For example:

acc=value

Indicator of the direction of the access of the VSAM data set. value can be "fwd" or "bwd".

blksize=value

Specifies the maximum length, in bytes, of a physical block of records.

byteseek

Indicator to allow byte seeks for a binary file. See also seek and tell in perlfunc.

lrecl=value

Specifies the length, in bytes, for fixed length records and the maximum length for variable length records.

recfm=A

ASA print control characters.

recfm=F

Fixed length unbloccked.

recfm=FA

Fixed-length, ASA print-control characters

recfm=FB

Fixed-length, blocked

recfm=FM

Fixed-length, machine print-control codes

recfm=FS

Fixed-length, unblocked, standard

recfm=FBA

Fixed-length, blocked, ASA print-control characters

recfm=FBM

Fixed-length, blocked, machine print-control codes

recfm=FBS

Fixed-length, unblocked, standard ASA print-control characters

recfm=FSA

Fixed-length, unblocked, standard, ASA print-control characters

recfm=FSM

Fixed-length, unblocked, standard, machine print-control codes

recfm=FBSA

Fixed-length, blocked, standard, ASA print-control characters

recfm=FBSM

Fixed-length, blocked, standard, machine print-control codes

recfm=U

Undefined-length

recfm=UA

Undefined-length, ASA print control characters

recfm=UM

Undefined-length, machine print control codes

recfm=V

Variable, unblocked

recfm=VA

Variable, ASA print-control characters

recfm=VB

Variable, blocked

recfm=VM

Variable, machine print-control codes

recfm=VS

Variable, unblocked, spanned

recfm=VBA

Variable, blocked, ASA print-control characters

recfm=VBM

Variable, blocked, machine print-control codes

recfm=VBS

Variable, blocked, spanned

recfm=VSA

Variable, unblocked, spanned, ASA print-control characters

recfm=VSM

Variable, unblocked, spanned, machine print-control codes

recfm=VBSA

Variable, blocked, spanned, ASA print-control characters

recfm=VBSM

Variable, blocked, spanned, machine print-control codes

recfm=*

Existing file attributes are used if file is opened in write mode.

Note: Using recfm=* is only valid for existing DASD data sets. It is ignored in all other cases.

rls=value

Indicates the VSAM RLS (Record Level Sharing) access mode in which a VSAM file is to be opened. This keyword is ignored for non-VSAM files. The following values are valid: "nri" - No Read Integrity, "cr" - Consistent Read

space

Space attributes for MVS data sets. Within the parameter you cannot have any embedded blanks.

type=memory

This parameter identifies this file as a memory file that is accessible only from C (or Perl) programs.

type=memory (hiperspace)

If you are using MVS/ESA, you can specify the HIPERSPACE suboption to open a hiperspace memory file.

type=record

This parameter specifies that the file is to be opened for sequential record I/O. The file must be opened as a binary file; otherwise, mvsopen() fails. Read and write operations are done with the sysread() and mvswrite() functions. This is the default mvsopen() mode for accessing VSAM clusters.

asis

Indicates that the file name is not to be converted to uppercase but used as is. This option is the default under POSIX. It is also the default for HFS file names.

password=sekrit

Specifies the password for a VSAM data set.

noseek

Indicates that the stream may not use any of the reposition functions. This may improve performance.

dynalloc() and dynfree() example ^

Here is an example of the use of dynalloc() and dynfree() with JCL DD card equivalent statements in comments on the right hand side:

    use OS390::Stdio qw(&dynalloc &dynfree);
    my %dyn_hash = (
        "ddname" => "MYDD",              # //MYDD DD
        "dsname" => "PVHP.MYDSN",        # //     DSN=PVHP.MYDSN,
        "status" => 4,                   # //     DISP=(NEW,   
        "normdisp" => 2,                 # //               CATLG),
        "alcunit" => '\001',             # //     SPACE=(CYL,
        "primary" => 2,                  # //             (2,
        "secondary" => 1,                # //               1),
        "misc_flags" => (2 | 8),         # //                RLSE,CONTIG),
        "dsorg" => 0x4000,               # //     DSORG=PS,
        "recfm" => 0x80 + 0x04 + 0x02,   # //     RECFM=FAM,
        "lrecl" => 121,                  # //     LRECL=121,
        "blksize" => 12100               # //     BLKSIZE=12100
    );
    if (dynalloc(\%dyn_hash)) {

        # use //'PVHP.MYDSN' data set

    }
    else {
        die "unable to dynalloc $dyn_hash{dsname}";
    }
    if (!dynfree(\%dyn_hash)) {
        warn "unable to dynfree $dyn_hash{dsname)}"
    }

Here is an example that allocates SPACE for being a PDS directory (with 3 directory cylinders):

    use OS390::Stdio qw(&dynalloc);
    if ( dynalloc (
           {  # <-- this curly brace creates an anonymous hash ref
        ddname =>    "ALLOC",        # //ALLOC DD
        dsname =>    "PVHP.MYPDS",   # //      DSN=PVHP.MYPDS,
        status =>    0x04,           # //      DISP=(NEW,   
        normdisp =>  0x02,           # //               CATLG,
        conddisp =>  0x04,           # //               DELETE),
        alcunit =>   '\x01',         # //      SPACE=(CYL,
        primary =>   2,              # //             (2,,
        dirblk  =>   3,              # //                3),
        misc_flags => (0x02 | 0x08), # //                RLSE,CONTIG),
        recfm =>     0x80 + 0x10,    # //      RECFM=FB,
        lrecl =>     80,             # //      LRECL=80,
        blksize =>   12100           # //      BLKSIZE=12100
           }  # close the anonymous hash ref
                  ) 
    {
        print "PDS allocated\n";
    }
    else 
    {
        warn "PDS not allocated"; 
    }

smf_record() tips ^

Note that calling smf_record() successfully may require authorization and/or special system set up. Setting up SMF is discussed in IBM document number GC28-1783-08 and UNIX system services access to SMF is also discussed in document number SC28-1890-08. Types, sub-types and record formats are discussed in the former document.

svc99() hash reference and text units ^

svc99() must be passed a hash reference with only certain keys allowed. One of the more important key/value pairs in the hash ref is the S99TXTPP text unit array reference. As an example consider the allocation of a data set like so (which assumes that PVHP is your HLQ):

    my $hash_ref = {(
    S99RBLN => 20,      # length of request block
    S99VERB => 1,       # verb for dsname allocation
    S99FLAG1 => 16384,  # do not use existing allocation
    S99TXTPP =>         # "text" units array ref
        [ (
       "\0\x02\0\x01\0\x0CPVHP.EXAMPLE",  # DSN=EXAMPLE 
       "\0\x05\0\x01\0\x01\x02",          # DISP=(,CATLG) 
       "\0\x07\0\0",                      # SPACE=(TRK,... 
       "\0\x0A\0\x01\0\x03\0\0\x14",      #  primary=20 
       "\0\x0B\0\x01\0\x03\0\0\x01",      #  secondary=1) 
       "\0\x30\0\x01\0\x02\0\x50",        # BLKSIZE=80 
       "\0\x3C\0\x01\0\x02\0\x40\0",      # DSORG=PS 
       "\0\x42\0\x01\0\x02\0\x50",        # LRECL=80 
        ) ],
               )};
    if (svc99($hash_ref)) {
        print "EXAMPLE was allocated.\n";
    }
    else {
        print "was unable to allocated DSNMAE=EXAMPLE\n";
    }

Note that the text units start with a null character then a key code number. For a listing of what these numbers should be consult the "//'SYS1.MACLIB(IEFZB4D2)'" member for a listing of relevant mnemonics. For example the UNIT is at x15 so that one could specify a UNIT=SYSDA with:

       "\0\x15\0\x01\0\x05SYSDA2",        # UNIT=SYSDA

Note that the last characters in a given array element are data, whereas the second to last may indicate the data field length. For example, if the above EXAMPLE allocation had been instead written with \x09 rather than \x0C as:

       "\0\x02\0\x01\0\x09PVHP.EXAMPLE",  # DSN=EXAM 

and if the call to svc99() succeeds with that, then "//'PVHP.EXAM'" would be allocated rather than "//'PVHP.EXAMPLE'".

REFERENCES ^

The discussion of mvsopen() modes was adapted from:

 EDCLB010: OS/390 V2R8.0 C/C++ Run-Time Library Reference
 Document Number SC28-1663-O5
 Table 21.  Values for the Positional Parameter
 Table 22.  Keyword Parameters for File Mode 

 OS/390 V2R8.0 MVS System Management Facilities (SMF)
 Document number GC28-1783-08

 OS/390 V2R8.0 UNIX System Services Planning
 Document number SC28-1890-08
 Chapter 16: Using SMF Records
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