Insulated DD attribute

To protect against accidental modification of a resource by other SVC 99 services, you can request that the system assign the insulated DD attribute. The insulated DD attribute is available on z/OS® 1.13 and later systems with APAR OA47824 installed.

To request the insulated DD attribute when dynamically allocating a resource, your program must be APF-authorized, in supervisor state, or running in PSW key 0 - 7. An allocation with the insulated DD attribute has the following characteristics:

• The convertible attribute cannot be assigned to the resource.
• The in-use attribute may not be removed from the resource.
• The permanently allocated attribute is assigned to the resource.

In order to dynamically unallocate a resource that was allocated with the insulated DD attribute, it is necessary to specify the corresponding insulated DD text unit in the dynamic unallocation parameter list. Any resource allocated with the insulated DD attribute will be unallocated at the end of the job step if it is not deallocated earlier.

When dynamically concatenating resources, it is not possible to create a group where some resources have the insulated DD attribute and some do not. If any resource in the group has the insulated DD attribute, all resources in the group must have the insulated DD attribute.

In order to dynamically concatenate a group of resources that were allocated with the insulated DD attribute, it is necessary to specify the corresponding insulated DD text unit in the dynamic concatenation parameter list. In order to dynamically deconcatenate a group of resources that were allocated with the insulated DD attribute, it is necessary to specify the corresponding insulated DD text unit in the dynamic deconcatenation parameter list.

Use of the insulated DD text units requires that your program be APF-authorized, in supervisor state, or running in PSW key 0-7. This effectively prevents unauthorized callers from unallocating, concatenating, or deconcatenating resources allocated with the insulated DD attribute.

It is an error to specify the insulated DD text units for a dynamic unallocation, concatenation, or deconcatenation request when the resource to be processed does not have the insulated DD attribute.

Dynamic remove in-use processing (verb code 05) is used to remove the in-use attribute of a resource. Since resources with the insulated DD attribute must always have the in-use attribute, dynamic remove in-use processing ignores any resources with the insulated DD attribute.

Dynamic ddname allocation (verb code 06) is used to assign the in-use attribute to an existing resource that does not have the in-use attribute assigned. Since a resource with the insulated DD attribute must also have the in-use attribute, the system rejects any attempt to assign the in-use attribute to a resource with the insulated DD attribute.

Additionally, the following services are not supported for resources with the insulated DD attribute:

• IEFDDSRV MODIFY, TYPE=ALLOCATION
• OPEN TYPE=J
• CLOSE with the FREE option