System Tables Subject to Skewing
Journal tables take the require spool and other transient storage from free space.
A common practice is to allocate a database with a certain amount of PERM, but never
use it. This ensures that there is free space for journals and so on. When your journal
tables are skewed, you get an error when running queries, letting you know the system
needs the journal space but cannot obtain it.
The DBC.AccessRights table is notorious for becoming skewed. If it grows too large,
it will affect the space limits dramatically. To reduce this skewing, either clean
up DBC.AccessRights by removing redundant rows or convert to using roles and then
remove the now redundant rows.
DBC.AccLogTbl table. Teradata Database generates at least one entry every time a user
defined for logging attempts to access an object. This table can grow very large and
consume a lot of disk space.
Resource usage logging tables or query logging tables. Consider daily offloading data
from the actual DBC tables into temporary staging tables and ultimately history tables
for analysis or archive.
Any table can becoming skewed if the primary index is poorly designed or if statistics
have not been collected and the Optimizer is using stale data. A usual tell-tale sign
is if one or more queries are doing a lot of maintenance on typically a single AMP.
If this happens, you need to track that query down and handle it like any other skewed