FNDU

Type

OMEGAMON Major command (Authorized)

Description

Finds all users of a device.

aFNDU device

a

An action character in column 1:

-

Specifies that new data be collected from the target address spaces.

␢

Enables minor commands to execute with previously collected data.

device

This can be:

xxxx

A 4-digit hexadecimal unit address

cccccc

6-digit volume serial number

If the unit indicated is online, FNDU accesses every active address space, and continues until it finds as many allocations as the UCBUSER field indicates. This can cause OMEGAMON to pause until all address spaces are examined.

For example, if you issue the command

-FNDU MVS001

or

-FNDU 0245

you might see the following result:

FNDU  MVS001  0245   2 User(s) Holding 3 Allocation(s) 

This typical FNDU display means that two users are active, and have three data sets allocated on MVS001 between them. To display the specific users, you must use the DSPA minor command of FNDU. If you reissue this command without the action character, it does not display current information. If, for example, you are attempting to determine allocations on paging volumes based on the PAOD exception, be sure to re-enter the action character.

When you try to vary a device offline, the VARY remains pending until all users of the device free their allocations. In the case of a DASD device, it is often difficult to determine which users have the data sets allocated. The z/OS® OS command, D U, and the OMEGAMON DALC minor command of DISK, show how many allocations are still held but not who holds them. The z/OS command D U,,ALLOC, displays the users of a volume but not the ddname or number of current allocations. The authorized command, FNDU, displays more detailed information than DALC or D U,,ALLOC.

Sometimes no allocations of a device are found, but the device use count shows a number greater than zero. This condition occurs in the following cases:

• At IPL time, the nucleus initialization program (NIP) allocates and opens several system data sets before the standard OPEN and ALLOCATE interface is available. To ensure that the volume is not forced offline, NIP raises the device use count by one for each data set it needs on a volume. Because there are no DD statements for these devices, FNDU does not find them under the main scheduler, and it appears that there is a discrepancy between DALC and FNDU. This affects the SYS1.LOGREC data set, the page and swap data sets, and all of the link list library data sets. Because you don’t want to vary these devices offline anyway, this does not present a problem.
• The other case is more serious. If you use the OS FORCE command or the OMEGAMON KILL command to cancel a user, the Recovery Termination Manager (RTM) does not perform any device allocation cleanup. Devices that the FORCEd user allocated do not have their use counts decremented, and so the volumes the job used show allocations that do not (and that FNDU cannot find). You cannot vary volumes in this condition offline, unless you use MZAP to zap the UCB USE count (UCBUSER) in memory.

The first time you use FNDU in an OMEGAMON session, it gets a work area to hold the collected data from the target address space. If you use FNDU in dedicated mode, you might have to increase the size of the OMEGAMON V=R region. If the allocation data from all of the active address spaces does not fit within the work area, FNDU issues a warning. Use the WSIZ minor of FNDU to increase the work area size and then reissue the FNDU command.

Related Information

Major of: DSPA, DSPC, DSPO, and WSIZ nn