Virtual UCB Management
Original Publication Date: 2008-Oct-25
Included in the Prior Art Database: 2008-Oct-25
Clients on z/OS are currently limited to a four digit device number. This severely limits the number of devices a client can have online at one time. One solution is to make larger volumes. Another solution is to dynamically manage the UCBs so that multiple devices can share the same real UCB. Our invention uses a dynamic UCB manager that creates virtual UCBs which are swapped into real UCBs when they are needed. When the operation using the UCB completes, the UCB manager marks that UCB as available to the next virtual UCB. This invention would be directed towards volumes which are not actively being used since they would be off-line a portion of the time.
Virtual UCB Management
In z/OS device ranges are setup in an HCD configuration file which describes what types of devices are allowed at virtual device addresses. For example tape devices are in a separate range than DASD devices. Also, some devices need to be online all the time, so those UCBs should not be altered. With our dynamic UCB manager, the user constructs the same HCD file, but provides additional information such as which range of devices should be considered swappable and which ranges are non-swappable. For UCB addresses that are to be swappable, the user will provide the list of devices that are to be swapped in and out. The swappable devices would have an additional two bytes added to the device number in our HCD, so the user can add over 64K devices. The number of swappable devices can exceed the number of available virtual device numbers. That additional two bytes only appears within the HCD, and does not affect other system components, since we use the traditional UCB, but swap which UCB the devices are assigned to. Non-swappable devices would be those that are more performance sensitive. Since there would be some overhead involved with swapping the UCBs, lower performance requirements would be needed for the swappable UCBs.
As non-swappable devices are varied online, the will be assigned non-swappable UCBs in accordance with the table setting. For those devices that have not yet been varied online, they...