Clearing a leftover Persistent Reserve reservation

You can clear leftover Persistent Reserve reservation.

Message number 6027-2202 indicates that a specified disk has a SCSI-3 PR reservation, which prevents the mmcrnsd command from formatting it. The following example is specific to a Linux® environment. Output on AIX® is similar but not identical.

Before trying to clear the PR reservation, use the following instructions to verify that the disk is really intended for GPFS use. Note that in this example, the device name is specified without a prefix (/dev/sdp is specified as sdp).

Display all the registration key values on the disk:
```
/usr/lpp/mmfs/bin/tsprreadkeys sdp
```
The system displays information similar to:
```
Registration keys for sdp
1. 00006d0000000001
```
If the registered key values all start with 0x00006d, which indicates that the PR registration was issued by GPFS, proceed to the next step to verify the SCSI-3 PR reservation type. Otherwise, contact your system administrator for information about clearing the disk state.

Display the reservation type on the disk:

/usr/lpp/mmfs/bin/tsprreadres sdp

The system displays information similar to:

yes:LU_SCOPE:WriteExclusive-AllRegistrants:0000000000000000

If the output indicates a PR reservation with type WriteExclusive-AllRegistrants, proceed to the following instructions for clearing the SCSI-3 PR reservation on the disk.

If the output does not indicate a PR reservation with this type, contact your system administrator for information about clearing the disk state.

To clear the SCSI-3 PR reservation on the disk, follow these steps:

Choose a hex value (HexValue); for example, 0x111abc that is not in the output of the tsprreadkeys command run previously. Register the local node to the disk by entering the following command with the chosen HexValue:
```
/usr/lpp/mmfs/bin/tsprregister sdp 0x111abc
```
Verify that the specified HexValue has been registered to the disk:
```
/usr/lpp/mmfs/bin/tsprreadkeys sdp
```
The system displays information similar to:
```
Registration keys for sdp
1. 00006d0000000001
2. 0000000000111abc
```
Clear the SCSI-3 PR reservation on the disk:
```
/usr/lpp/mmfs/bin/tsprclear sdp 0x111abc
```
Verify that the PR registration has been cleared:
```
/usr/lpp/mmfs/bin/tsprreadkeys sdp
```
The system displays information similar to:
```
Registration keys for sdp
```
Verify that the reservation has been cleared:
```
/usr/lpp/mmfs/bin/tsprreadres sdp
```
The system displays information similar to:
```
no:::
```

The disk is now ready to use for creating an NSD.