16.10 - WDB - Teradata Database

Teradata Database Support Utilities

prodname
Teradata Database
vrm_release
16.10
created_date
June 2017
category
Configuration
featnum
B035-1180-161K

Purpose

The WDB (WAL Data Block) command displays WAL log data blocks.

Syntax

The online help lists the display options (/P, /S, /M, /L, /H, /X, /V) as /dispopt. You can type the options at the beginning or end of the command.


/P
Positions to the WDB. If one does not exist, an error occurs. Nothing is displayed unless there is a problem.
/S
Displays the header, trailer, and the first and last generic WAL log record headers.
/M
Displays all of the generic WAL log record headers, in addition to the information displayed by the /S option.
/L
Displays the type-specific WAL log record headers for NONTJ and TJ records, in addition to the information displayed by the /M option.
/H
Displays the header followed by the entire WDB in hexadecimal.
/X
Displays the change data (before and after images) in hexadecimal, in addition to the information displayed by the /L option.
/V
Verifies that the WDB is logically correct, but does not display it.
FORCE
Attempts to format and display the segment as a WDB, even if the block type does not indicate a WDB.
cylid
The 64-bit identifier of a cylinder, entered as a 16-character hexadecimal number.
sectornum
The sector number.
sectorcount
The sector count.
=
Specifies that Filer should use the most recently saved values for cylid, sectornum, or sectorcount.
This option cannot be used unless input values have already been defined for cylid, sectornum, or sectorcount. For more information, see Stored Input Values.

Usage Notes

The checksum in the WDB is intended to cover the time between writing the WDB to disk and having filled the cylinder, finally writing the WCI and its WDBs to disk. The WCI is written once when the cylinder is initialized and once when the cylinder is full. The WCI is not written as each WDBD is added to the WCI in memory. In reading the WDBs in the last log cylinder after a restart that lost cache, no WDBDs with external checksums exist on the disk; therefore, internal checksums in the WDBs are used to validate the WDBs.