The DEFERRED_SEGMENT_CREATION parameter is set TRUE in your database instance. (erfasst) You execute the following command to create a table: SQL> CREATE TABLE acctl (ac_no NUMBER, ac_desc varchar2(25

When a CREATE INDEX statement is executed on a table that was created with deferred segment allocation, Oracle immediately allocates a segment for that index as part of the explicit index creation operation, regardless of the deferred setting on the parent table.

The table is created without a segment because DEFERRED_SEGMENT_CREATION=TRUE defers segment allocation; the absence of a storage clause is entirely irrelevant to this behavior.

With DEFERRED_SEGMENT_CREATION=TRUE, the table's data segment is automatically created when the first row is inserted, because Oracle requires a physical segment before it can store any row data.

While ALTER TABLE...ALLOCATE EXTENT can force segment creation, the question's identified correct answers are the two automatic triggers - first row insert and explicit index creation - that are integral to the deferred segment creation feature design.

Extents are not immediately allocated at CREATE TABLE time when DEFERRED_SEGMENT_CREATION=TRUE; the entire purpose of the parameter is to defer all segment and extent allocation until data is actually written.