October 2011
Intermediate to advanced
510 pages
18h 48m
English
book
IBM IMS Version 12 Technical Overview
by Paolo Bruni, Isabelle Bruneel, Angie Greenhaw, Dougie Lawson, Jorge Alberto Luz Ribeiro, Egide Van Aershot
Content preview from IBM IMS Version 12 Technical Overview
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54 IBM IMS Version 12 Technical Overview
2.7.2 Description of EAV
An EAV is a volume with more than 65,520 cylinders. An EAV increases the amount of
addressable DASD storage per volume beyond 65,520 cylinders by changing how tracks on
ECKD volumes are addressed.
A track address is a 32-bit number that identifies each track within a volume.
The address is in the format hexadecimal CCCCcccH where:
CCCC The low order 16-bits of the cylinder number.
ccc The high order 12-bits of the cylinder number.
H The four-bit track number.
The combination of the 16-bits and 12-bits for the low order and high order cylinder number
represents a 28-bit cylinder number.
For an EAV, the EAS is cylinders whose addresses are equal to or greater than 65,536. The
ccc ...
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