In dbc.objectusage Teradata logs how often objects are accessed by SQL statements and the information is used by optimizer for stats extrapolation (Object Use Count aka OUC).
Checktable may report 2791 or 2778 errors like shown below on table dbc.objectusage.
This is caused by a problem where a correct OUC which is logged in the primary data row does not match an incorrect OUC which is logged in the fallback data row.
Since the access count of the objects is correct in the primary data row there is no impact to the operation of the system, because the fallback data row would never be accessed on a system which is up and running.
Also Change Control activities (upgrades, migrations, reconfig, etc.) are not impacted by this problem.
Example 2791 error from checktable level two:
"DBC"."OBJECTUSAGE" checking at 12:11:16 17/02/13.
Table id 0000H 0121H
2791: Primary and fallback data row checksums do not match.
Primary AMP 00132
Fallback AMP 00024, Fallback subtable 2048 (800H)
Row id 0000000000000000 C162H D786H 0000H 0002H
Example 2778 error from checktable level three:
Table: "DBC"."OBJECTUSAGE" checking at 10:39:39 16/11/19.
Table id 0000H 0121H, Database id 0000H 0001H, Fallback.
2778: Primary and fallback data rows do not match.
Primary AMP 00042
Fallback AMP 00090, Fallback subtable 2048 (800H)
Row id 0000000000000000 07E7H B63CH 0000H 0001H