DFSMSdss: Determine whether you need DISABLE(REFUCB) in parmlib member DEVSUPxx
Description
With z/OS V2R2, the automatic refresh UCB (REFUCB) function of the Device Manager is enabled by default. Previously, it was disabled by default. If you want the function to be disabled, you must explicitly disable it by using the statement DISABLE(REFUCB) in parmlib member DEVSUPxx.
ICKDSF FLASHCPY, INIT, and REFORMAT commands, and DFSMSdss full volume COPY and RESTORE functions, might update the volume serial and location of the volume table of contents (VTOC). This behavior can present a problem when the device is online to other systems. To address this problem, the automatic refresh UCB function (REFUCB) was introduced in z/OS V1R13, and is controlled by DISABLE | ENABLE(REFUCB) in parmlib member DEVSUPxx. DISABLE(REFUCB) was the default.
Table 1 provides more details about this migration action. Use this information to plan your changes to the system.
| Element or feature: | DFSMSdss |
|---|---|
| When change was introduced: | z/OS V2R2 |
| Applies to migration from: | z/OS V2R1 and z/OS V1R13. |
| Timing: | Before installing z/OS V2R2. |
| Is the migration action required? | Yes, if you require the automatic refresh UCB function to be disabled. Note that the automatic refresh UCB function is only applicable to volumes that are shared with other systems in the same sysplex. |
| Target system hardware requirements: | None. |
| Target system software requirements: | None. |
| Other system (coexistence or fallback) requirements: | None. |
| Restrictions: | None. |
| System impacts: | For each system that has enabled the REFUCB function, an unconditional VARY ONLINE to the device is performed when the system is notified that the volume serial, the VTOC location, or both, has changed since the device was last varied online. This action updates fields in the UCB, including the volume serial (UCBVOLI) and the start location of the VTOC (UCBVTOC). If the VARY ONLINE,UNCOND fails for the device, or if the VARY ONLINE,UNCOND is not performed because the REFUCB function is not enabled on a system in the sysplex, the following write-to-operator (WTO) message is written to the system console: DMO0063E dddd,volser, UCB NOT UPDATED REFUCB=[Y/N],USERS=xxxx. |
| Related IBM® Health Checker for z/OS® check: | Use check IBMDMO, DMO_REFUCB to determine whether the REFUCB function is disabled by the system. This check is provided as of z/OS V2R2. For more information, see IBM Health Checker for z/OS User's Guide. |
Steps to take
If you determine that you need the automatic refresh UCB function to be disabled, review your current parmlib member DEVSUPxx. If DISABLE(REFUCB) is not present, add DISABLE(REFUCB). If ENABLE(REFUCB) is present, delete it.
Reference information
For information about enabling or disabling the automatic refresh UCB function, see the description of parmlib member DEVSUPxx in z/OS MVS Initialization and Tuning Reference.