Purpose
There are two copies of each WCI, only one of which is active at any time. The active copy reflects the current state of the WAL cylinder. The ALTWCI command makes the non-active copy the active copy, and the formerly active copy the non-active copy.
This command can be used only when Teradata Database is not running on the affected AMP.
Syntax
- cylid
- The 64-bit identifier of a cylinder, entered as a 16-character hexadecimal number.
Usage Notes
ALTWCI can be used only when the scope is set to one vproc. For more information on the SCOPE command, see SCOPE (or VPROC).
Picking the alternate copy of a WCI might result in overlapping record numbers across cylinders and mismatches between the WCI and the blocks on the associated cylinder. After performing this command, use scandisk to determine whether additional repairs are required.
Example: Filer ALTWCI command
Filer ==> scope vproc 0 Command has been sent to Slave tasks. Tue Jul 03, 2007 16:47:39 1 of 8 amps have been selected Filer ==> altwci 0 2A Active WCI --------- Location: PRIMARY Blk Code: WCI Version Number: 19 WLSN : (0000000000024E32) Stamp : Wed Jul 11, 2007 15:28:36.51 (64 2F 95 46 33) Non-Active WCI ------------- Location: SECONDARY Blk Code: WCI Version Number: 3 WLSN : (000000000000AF68) Stamp : Tue Jul 03, 2007 10:51:10.01 (5E 62 8A 46 01) *** WARNING *** Picking the alternate copy of a [W]CI might result in overlapping tableids/rowids across cylinders and mismatches between the [W]CI and the blocks on the associated cylinder. After performing this command, use scandisk to determine whether additional repairs are required. *** WARNING *** Do you want to switch the active copy to the alternate copy? (Y/N) > y y Active WCI --------- Location: SECONDARY Blk Code: WCI Version Number: 3 WLSN : (000000000000AF68) Stamp : Tue Jul 03, 2007 10:51:10.07 (5E 62 8A 46 07) Successfully alternated the WCI.