When user tries to access data from any table Teradata applies read lock on that table. We can see from the explain plan of the query- Explain sel * from mydb.teradatapoint; 1) First, we lock a distinct mydb.”pseudo table” … Read more »
All the objects in the database are shared among variety of users who are accessing the data in parallel. For example, one user is updating a table and if another user tries to access that table at the same time, … Read more »
Down-AMP Recovery Journal:- Recovery journal provides the capability to continue normal write operation like insert, update, create and delete on a table even if a logical AMP goes down in the same cluster. Suppose we have activated the fallback option … Read more »
The permanent journal in Teradata provides the capability to capture the snapshot of the table/tables before and after applying changes using DML statements like insert, delete and update. Unlike transient journal which capture the snapshot of table before applying changes … Read more »
As the name suggests, No primary index table means there will be no primary index defined on Teradata table. This feature has been introduced in V2R13 release. The main purpose of this feature which allows us to create tables with … Read more »
We have two types of tables in Teradata, SET and Multiset table and the main difference of these table is SET table doesn’t allow duplicate row whereas Multiset table allows it, as below: A set table does not allow any … Read more »
There are mainly three types of spaces in Teradata. These are: Permanent Space. Spool Space. Temporary Space. Let us understand in brief about them. PERMANENT SPACE (Perm Space):- This is the space where objects such as databases, users, tables, … Read more »
Partitioned Primary Index (PPI) is one of the powerful feature of Teradata which allows a user to access a part of the table rather than full table access. This helps in improving the performance as full table scan is eliminated. … Read more »
Hash index in Teradata has been designed to improve the performance of Teradata query in a way similar to the Single Table Join Index, which restricts parsing engine not to access or redistribute the base table. It may act like … Read more »
A join index is an indexing structure containing columns from multiple tables, specifically the resulting columns from one or more tables. Rather than having to join an individual table each time the join operation is needed, the query can be … Read more »