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Sequentially reads a physical block of user-specified size from a KSAM/XL file.
Syntax
I32 REC I32 A I32
lgth := AIFKSMREAD ( overall_status, filenum, buffer, bytes,
I32
user_id );
Functional Return
- lgth
- 32-bit signed integer by reference (required)
Returns a positive integer value indicating the length of the
information transferred.
Parameters
- overall_status
- record by reference (required)
Returns the overall status of the call. A zero indicates a successful
call. A negative value indicates an error in the overall call. Refer to
appendix A for meanings of status values.
- filenum
- 32-bit signed integer by value (required)
An identifier supplying the file number of the file to be read.
- buffer
- character array by reference (required)
An array to hold a physical block of the KSAM/XL file. The content in
the buffer returned from the first AIFKSMREAD after the KSAM/XL
file is opened is used by AIFKSMCREATE to duplicate a KSAM/XL
file. The contents returned from subsequent AIFKSMREADs are
used by AIFKSMWRITEs to copy to the new KSAM/XL file.
The minimum buffer size is 10,240 bytes.
- bytes
- 32-bit signed integer by value (required)
A positive integer specifying the number of bytes to be transferred. If
this value is zero, no transfer occurs. If bytes is
larger than the remaining physical block size, transfer is limited to
the length up to EOF.
- user_id
- 32-bit signed integer by value (optional)
The user ID assigned to a vendor at the time of purchase of the
Architected Interface Facility: Operating System product.
Operation Notes
The AIFKSMREAD call reads a block from a KSAM/XL file in its physical
sequence. The KSAM/XL file must have been opened in copy mode with MR
and NOBUF options and read-only access in order to call this
procedure. The first AIFKSMREAD after the file is opened transfers
all of the necessary information required by AIFKSMCREATE. The buffer
size and the bytes count must be large enough to hold the information to be
passed to AIFKSMCREATE. The minimum size required may vary depending
on the size of user labels. In the case where no user label exists in the file,
the minimum size required is 10240 bytes. It is recommended that the buffer
size and the bytes count be multiples of 4096 and 65536 bytes (16 pages). At
the end of AIFKSMREAD procedure, the data pointer is positioned to
the byte following the last byte being read. AIFKSMREAD transfers
only the in-use areas and ignores the unused area in the KSAM/XL file. An
end-of-file status is returned if AIFKSMREAD is called after the last
byte of the file is transferred.
The AIFKSMREAD procedure returns a positive integer value to
lgth showing the length of the information transferred. Both
lgth and bytes in the AIFKSMREAD call
must be positive numbers representing bytes counts.
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