Maximum size of a Global Variable Table
Each Global Variable Table (GVT) is stored as a single record in the INDEX operational data set (VSAM KSDS).
There is an upper limit to the overall size of the largest GVT allowed, or 32760 bytes.
Here are the sizes of the various elements stored in a GVT:
Fixed overhead (table header + hash table) = 284 bytes
Name element (1 per variable) = 21 bytes
Variable name = 64 bytes max
Attribute element (1 per variable) = 40 bytes if the length of the variable value = or < 4 or
40 bytes + length of the variable value rounded up to next multiple of 8.
Trigger element (1 per trigger):
with Event target = 60 + (length of match string) + 1
with WOB target = 44 + length of AFM (if match string specified- optional)
Trigger link element (1 per variable/trigger pair) = 16
Use the VTLIST command to display one or more Global Variable Tables.
The amount of free space reported by VTLIST represents the total length of unoccupied space in the GVT. This might not be one contiguous space.
When a new variable is added, ESP Edition tries to search for contiguous space among the unoccupied space.
The Table Size reported by VTLIST represents the next available byte offset. This is the offset in the GVT record where the new variable and its header will be placed.
There must be enough space from this offset to the end of the record.