Shared memory storage requirements
Shared memory is a type of virtual storage that allows
multiple address spaces to easily address storage that is common to DB2® address spaces.
This memory resides above
the 2 GB bar.
The shared memory object is created at DB2 startup, and all DB2 address spaces for the subsystem (DSN1DIST, DSN1DBM1, DSN1MSTR, and Utilities) are registered with z/OS® to be able to access the shared memory object.
To define the size of the shared memory and the 64-bit common area, use the HVSHARE and
HVCOMMON parameters of the IEASYSxx member in the parmlib concatenation.
Restriction: Ensure that you have defined a high enough value for HVSHARE to satisfy all
component requests for shared memory within the z/OS image.
The default value is 510 TB. DB2 10 requires 160 GB of contiguous 64-bit
shared private storage for each subsystem above the 2 GB bar. This storage is virtual, and it
is controlled by the z/OS HVSHARE parameter in IEASYSxx. This
storage is not backed at allocation, only as it is used.
DB2 10 requires 160 GB of contiguous 64-bit
shared private storage for each subsystem above the 2 GB bar. This storage is virtual, and it
is controlled by the z/OS HVSHARE parameter in IEASYSxx. This
storage is not backed at allocation, only as it is used. 
IFCID 0225 has statistics that you can use to determine the amount of currently
defined storage and how much of it is currently allocated.
