Hi,I know fastexport can set multiple sessions,but i don't know how does these sessions work, for example ,I want to export data from a table ,so i submit a "select * from table_name" in the fastexport script and set 4 sessions,I think a SQL statement is a request and a request is send to a PE,and a PE is one to one correspondence to a session ,so just a session is working ,other 3 sessions is idle?
I have a similar question. We use TPT Protocoll (via Datastage using 4 partitions) for exporting data and when i look at PMON i can see 4 times (4 sessions) the same "SELECT * FROM <TABLE>" running...
I understand that Datatstage has partitioned Datasets which are receiving the data but why 4 sessions with exactly the same select statement?
The actual fetching of data from the database is done by a single session however it is really the return of the data to the user that those multiple sessions come handy in. They return the data in parallel back to the user and provide the efficiency over a simple select.
If you are using DataStage then you are most likely using TPTAPI.
The TPTAPI operator to which you are referring is the Export operator, and that operator behaves like FastExport. The operator connects a SQL session and then data sessions.
If you have request "4 sessions" then that refers to the data sessions.
The SELECT statement is sent on the SQL session. The data is retrieved on the special protocol data sessions.
The SELECT statement is not sent to Teradata on those data sessions.