The following process is a simple way to change the map a table uses:
- Query the view TableToSparseMapSizingV(X). This view recommends a map for each table and identifies when the current map should be changed.For example, the following request produces a list of tables that Teradata recommends use a sparse map but are now using a contiguous map:
SELECT DatabaseName, TableName FROM TDMaps.TableToSparseMapSizingV WHERE RecommendedMap LIKE '%Sparse%' AND CurrentMapKind = 'C';
The following request produces a list of tables that Teradata recommends use a different map type (either sparse or contiguous) than what they are using now:SELECT DatabaseName, TableName FROM TDMaps.TableToSparseMapSizingV WHERE MapOk = 'N';
- If you decide that a table should use a different map, either issue an ALTER TABLE request to name a different map for the table or use the Mover stored procedure, which is described later in this chapter. To use ALTER TABLE, you must have the DROP privilege on the table you want to alter. For more information on the ALTER TABLE request for maps, see SQL Data Definition Language - Syntax and Examples.