What is pseudo lock in Teradata?
This is called DEADLOCK situation. Teradata uses Pseudo Lock mechanism to avoid this kind of deadlock situation. Whenever users submit SQL to access any table, Teradata will assign one AMP to inform other AMPs for locking the particular table in all AMPs. This AMP is known as gatekeeper AMP.
What is pseudo lock?
If you have pseudo knee locking, you feel as though you can’t move your knee because you are in so much pain. However, there isn’t something in your knee actually preventing you from moving your leg. This is your body causing a muscle spasm triggered by pain in or near your knee.
What are the different types of locks in Teradata?
There are four types of locks:
- Exclusive : prevents any other type of concurrent access.
- Write : prevents other reads, writes, exclusives access.
- Read : prevents writes and exclusives access.
- Access : prevents exclusive access only.
How do I know if a table is locked in Teradata?
To check whether a table is locked or not in Teradata
- Lock Table DBNAME. TABLENAME write nowait.
- Select * from DBNAME. TABLENAME;
What is a pseudo table?
A pseudo column behaves like a table column, but is not actually stored in the table. You can select from pseudo columns, but you cannot insert, update, or delete their values.
What is lock row for access in Teradata?
What is locking in Teradata? Locking database objects is a must in RDBMS to avoid multiple users changing and accessing the same data simultaneously in a way that is causing data inconsistencies. In other words, the affected objects are locked to ensure integrity whenever a user is accessing or changing data.
What is pseudo knee locking?
Pseudo locked knee occurs when severe knee pain triggers the knee muscles to spasm and contract. It is an automatic defense mechanism that the body uses to discourage movement of the knee. Restricting the knee in this way helps prevent further damage.
Which type of lock is automatically placed for an insert in Teradata?
Teradata has dedicated lock manager to automatically lock at the database, table and row hash level. Database Lock: Lock will be applied to all the tables and views. Table Lock: Lock applied to the all rows in table/view. Row hash Lock: Single or multiple rows in a table will be locked.
What is locking row for access in Teradata?
What is pseudo table in SQL?
A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. A pseudocolumn is also similar to a function without arguments (please refer to Chapter 5, “Functions”.
Which are Pseudocolumns examples?
Some of the important Pseudo Columns are as follows:
- NEXTVAL in SQL. With the help of Nextval pseudo column we get the flexibility to increment the sequence.
- CURRVAL in SQL.
- SYSDATE in SQL.
- SQL ROWNUM.
- ROWID in SQL.
- USER in SQL.
At which level does locking supported by Teradata?
row level
Teradata usually locks at the row level. SAS/ACCESS lock options can lock at the row, table, or view level. A change in the scope of a lock from row to table affects concurrent access to DBMS objects.
How do you fix a pseudo knee lock?
In pseudo locked knee, the knee is physically capable of moving, but the person cannot move it due to severe pain or swelling. Both types of locked knee typically require pain medications, ice, and rest. A doctor may also recommend physical therapy to help restore movement in the knee joint.
What is FastLoad and MultiLoad?
FastLoad can sort the incoming rows directly into the target table, whereas MultiLoad first sorts the incoming rows into a worktable and then applies the worktable to the target table. MultiLoad fully supports mulltiset tables with duplicate rows.
What is TPT Teradata?
Teradata Parallel Transporter aka TPT is new generation utility tool aim to create one stop tool for all the activities related to loading and exporting of date from/to Teradata database. Teradata advise to prefer TPT over existing utilities such as fastload, fastexport, multiload & tpump.
Teradata uses Pseudo Lock mechanism to avoid this kind of deadlock situation. Whenever users submit SQL to access any table, Teradata will assign one AMP to inform other AMPs for locking the particular table in all AMPs.
How to lock data in Teradata?
Teradata has dedicated lock manager to automatically lock at the database, table and row hash level. Database Lock: Lock will be applied to all the tables and views. Table Lock: Lock applied to the all rows in table/view. Row hash Lock: Single or multiple rows in a table will be locked.
How to prevent data inconsistency in Teradata?
To prevent this kind of data inconsistency locking mechanism has been invented. Teradata has dedicated lock manager to automatically lock at the database, table and row hash level. Database Lock: Lock will be applied to all the tables and views. Table Lock: Lock applied to the all rows in table/view.
What is the pseudo table mechanism?
The pseudo table mechanism is a way to serially queue all table level locks through the use of an internal pseudo table. In this table the database locks the row hash of the table’s table ID. It is a false lock which is applied on the table to prevent two users from getting conflicting locks with all-AMP requests.