Re: Creating big indexes

 You can first create the index on the table using the "On ONLY"keyword, something as below.

CREATE INDEX idx ON ONLY tab(col1);

Then create indexes on each partition in "concurrently" from multiple sessions in chunks.

CREATE INDEX CONCURRENTLY idx_1    ON tab_part1(col1);
CREATE INDEX CONCURRENTLY idx_2    ON tab_part2(col1);

After this step finishes the table level index which was created in the first step will be in valid state automatically.