System tables uses to track the database objects. In essence, access is a set of relational database tables (the system tables) about a set of relational database tables (the user project). System tables should not be altered directly by any user. For example, do not attempt to modify system tables with DELETE, UPDATE, or INSERT statements, or user-defined triggers.
System tables are much like the tables you create in a database – with a few exceptions. First, they are identified internally as system objects so that you can differentiate your regular tables from system tables. Secondly, some system tables are inherently read-only. System table are documented here solely for the purpose of giving us a better understanding of how Teradata RDBMS works internally. The following table describes each of the system tables.
DBC.TVM
Describes each table, view, or macro on the Teradata RDBMS. Identify table.
DBC.TVFIELDS
Describes each column on the Teradata RDBMS.
DBC.User
Identify user.
DBC.ACCESSRIGHTS
Describes each database and userid on the Teradata RDBMS.
DBC.DBASE
Describes each database and userid on the Teradata RDBMS. Identify database.
DBC.INDEXES
Describes columns contained in indexes in the Teradata RDBMS.
DBC.ResUsage
Log resource usage data.
Example
SELECT ACCOUNTNAME, USERNAME, SUM(CPUTIME), SUM(DISKIO) FROM
DBC.AMPUSAGE
WHERE SUBSTR(ACCOUNTNAME, 1, 2) = ‘CB’
GROUP BY USERNAME, ACCOUNTNAME
ORDER BY USERNAME, ACCOUNTNAME;
*** Query completed. 9 rows found. 4 columns returned.
*** Total elapsed time was 2 seconds.
AccountName UserName Sum(CpuTime) Sum(DiskIO)
————– ————- —————— —————
CB990902 JANETJONES 1,498.64 3,444,236
CB990903 JANETJONES 934.23 1,588,764
CB990904 JANETJONES 883.74 924,262
CB990905 JANETJONES 214.99 200,657
CB990902 JOHNSMITH 440.05 396,338
CB990903 JOHNSMITH 380.12 229,730
CB990904 JOHNSMITH 112.17 184,922
CB990905 JOHNSMITH 56.88 99,677
CB990902 SAMOREILLY 340.34 410,178