Accessing Large VSAM Files

You might find that VSAM files larger than 1GB (gigabyte) cannot be accessed. This is because the default record locking mechanism uses the top two bits of the file address for locking and compression bits, thus reducing the address space for the maximum offset from 4GB to 1GB for a shared idxformat 3 or 4 file. If you encounter this problem, you should change the record locking mechanism for the file. To do this:

1. If the large VSAM files are set to OPEN (which means that the files are opened when the CICS region is started), verify that Fileshare Support on the SIT is enabled.
2. Create a file handler configuration file that sets LOCKTYPE to 2 for the files causing the problem. With this setting, the file handling mechanism creates a separate file for storing record locks, with the same basename as the file and a .lck extension.
3. Set the EXTFH environment variable to point to the file. The default file name is extfh.cfg.

The file handler configuration file lists defaults for all files under the tag [XFH-DEFAULT], and settings for individual files under a tag consisting of the filename. For example, the following configuration file sets BASENAME=ON (which means that you do not need to supply pathnames for files) and sets the lock type to 2 for the file myfile:

[XFH-DEFAULT]
BASENAME=ON
[MYFILE]
LOCKTYPE=2