CHANGEACCESS request

To request that the type of access to the specified virtual storage be changed, use the CHANGEACCESS request. The three types of access are:

READONLY
SHAREDWRITE
HIDDEN

The scope of the change is determined by your choice of LOCAL or GLOBAL on the CHANGEACCESS parameter of the GETSHARED service. When CHANGEACCESS=LOCAL is specified or defaulted on the CHANGEACCESS parameter of the GETSHARED service, only the address space specified by the ALET parameter on the CHANGEACCESS service is affected. If the shared memory object is not addressable by this address space because the IARV64 SHAREMEMOBJ request was not issued, the request will fail.

When the CHANGEACCESS=GLOBAL is specified on the CHANGEACCESS parameter of the GETSHARED service, all address spaces currently sharing the memory object are affected, so all address spaces will get the same view. Subsequent IARV64 SHAREMEMOBJ requests for this memory object will also be affected until the next CHANGEACCESS invocation. Memory objects with CHANGEACCESS=GLOBAL support CHANGEACCESS requests without prior SHAREMEMOBJ requests.

CHANGEACCESS requests for memory objects specified as CHANGEACCESS=LOCAL require that the target space have interest in the shared memory object, which means a SHAREMEMOBJ for the target space must be done before the CHANGEACCESS request. Because CHANGEACCESS changes the view of the specified address space you must have access to memory object before you can CHANGEACCESS.

Parameters for the IARV64 CHANGEACCESS service include:

VIEW specifies the type of access you want to have to the virtual storage. The three types of access are READONLY, SHAREDWRITE, or HIDDEN.
RANGLIST specifies the virtual address which can be anywhere in the shared memory object. The following rules apply:
- The starting address must be on a segment boundary.
- The starting address must be within a memory object returned by a GETSHARED request.
- A single range must be contained within a single memory object.
ALETVALUE=aletvalue indicates the ALET of the address space that will access the memory object.
NUMRANGE specifies the number of entries in the supplied range list.

For an example of this request, see Example of changing the access of a shared memory object – CHANGEACCESS.