Oracle 11g how to estimate needed TEMP tablespace?

Question

We do an initial bulk load of some tables (both, source and target are Oracle 11g). The process is as follows: 1. truncate, 2. drop indexes (the PK and a unique index), 3. b

Answer 1

This is a good question.

First, If you create the following primary key

alter table TARGET_SCHEMA.MYBIGTABLE 
     add constraint PK_MYBIGTABLE primary key (MYBIGTABLE_PK)

then you should query

explain plan for 
     select PK_MYBIGTABLE 
     from SOURCE_SCHEMA.MYBIGTABLE 
     group by PK_MYBIGTABLE 

To get an estimate (make sure you gather stats exec dbms_stats.gather_table_stats('SOURCE_SCHEMA','MYBIGTABLE').

Second , you can query V$TEMPSEG_USAGE to see how much temp blocks were consumed before you got thrown and v$session_longops to see how much of the total process you finished.

Oracle docs suggests creating a dedicated temp tablespace for the process to not disturb any other operations.

Please post an edit if you find a more accurate solution.