The OPEN macro and the access methods are only affected by the introduction of large files, not by the introduction of large volumes.
The OPEN interface checks whether files are permitted to extend beyond 32 GB and whether the creation of files >= 32 GB and access to such files are permitted.
There are two aspects associated with this:
Rejection of access to or the creation of large files for access methods that do not allow processing of large files.
Indication that a program can create or open files >= 32 GB.
Incompatible interface variants
Interfaces where 3-byte block numbers are used are never able to work with files >= 32 GB. This affects the following cases:
All files in key format (BLKCTRL=PAMKEY):
The logical block numbers in the PAMKEY are only 3 bytes wide.24-bit interface of UPAM
The field for logical block numbers in the UPAM parameter lists and in the TU FCB is only 3 bytes wide.24-bit interface of SAM
The logical block numbers are affected as part of the retrieval address.24-bit interface of ISAM
In all the cases described above, the following applies:
Access to files >= 32 GB is rejected with the return code
X'00000D9D'orX'00000D00', depending on the size of the storage space allocated to the file (FILE_SIZE).Exceeding a file size of 32 GB as a result of secondary allocation is prohibited (LARGE_FILE).
Semantic incompatibilities
It is possible that applications use interfaces that employ 4-byte fields for the data fields described above, but that these 4-byte fields are implicitly or explicitly subject to the former limitation to values less than X'00FFFFFF'. Detailed information relating to this can be found in the Appendix, in the section "Semantic incompatibilities".
The following return codes display information about execution of the macro with regard to large files:
X'cc' | X'bb' | X'aaaa' | Explanation |
X'00' | X'00' | X'0D9D' | Error when opening a disk file |
X'00' | X'00' | X'0D00' | System error when opening a file |