Defining an above 16 megabyte UCB

You can use HCD to define a device's UCB above 16 megabytes if the device's unit information module (UIM) indicates that the device support code enables above 16 megabyte UCBs. If the device support code supports above 16 megabyte UCBs, the LOCANY parameter appears on the HCD Define Device Parameters / Features panel. Specify a value for the LOCANY device parameter to either:
  • Define a device's UCB below 16 megabytes only (LOCANY is No). The UCB cannot reside in 31-bit storage.
  • Define a device's UCB above 16 megabytes (LOCANY is Yes). The UCB can reside in 31-bit storage.

The default for LOCANY ( if it is not specified by the UIM) is No. This can be overwritten by including the option OS_PARM_DEFAULT = LOCANY,YES in the HCD profile.

You can dynamically change the definition of a UCB. To dynamically change a definition from below 16 megabytes to above 16 megabytes, change the LOCANY parameter value from "No" to "Yes" and activate the new IODF in software-only mode.