CA Dynam for VSE User Guide

Direct Access File Independence Facility (VCKD)
In general, the number of FBA blocks to allocate for each CKD track can be
calculated using the following formula:
(NRPT * KDL) + 4 + (3 * NRPT)
FBABLKS = -----------------------------
KDL
NRPT
512
= key length + data length
rounded high
= number of records per track for the disk type and
specified KDL
FBABLKS = number of FBA blocks to allocate per CKD track
Note that the number of allocated FBA blocks on the EXTENT statement
must be an even multiple of the number of FBA blocks that define an
emulated CKD track. Therefore, 1500 FBA blocks will define 100 CKD
tracks.
For example, on a 3340 device, a record size of 2552 bytes produces three
blocks per track totaling a maximum of 7656 bytes. Therefore, VCKD will
allocate 15 FBA blocks for each CKD track. The allocation is calculated as
follows:
(3 * 2552) + 4 + (3 * 3) 7656 + 4 + 9 7669
------------------------ = ------------ = ---- = 15 (when rounded up)
512 512 512
• Using VCKDANAL
Another method to obtain the number of blocks to allocate for each CKD
track is to run the VCKD disk file analyzer program VCKDANAL. This
program will read the first track of your CKD DA file and compute the
required number of FBA blocks to allocate for each track. For more
information, see VCKDANAL.
Creating FBA Disk Files
You can use any of the following methods to create the new Direct Access file
on the FBA disk:
• Format the FBA disk extent using the VCKD Clear Disk Program
(VCKDCLDK). Then restore the file with a user-written backup/restore
program that utilizes DTFDA LIOCS.
• Restore the file with a user-written program that performs WRITE RZERO
and WRITE AFTER formatting writes.
• Use the VCKD backup/restore program (VCKDBKRS) to copy the CKD file
to tape. Then restore the tape to the FBA disk.
Chapter 6: Controlling File Independence 6–47