Final answer:
An autonomous data warehouse (ADW) is optimized for complex SQL queries (option 2) and gathers statistics as part of DML operations (option 4). It is designed for operational efficiency and to reduce the administrative workload.
Step-by-step explanation:
The question pertains to the characteristics of an autonomous data warehouse (ADW). An autonomous data warehouse is designed to reduce the complexity of managing a data warehouse while improving efficiency and reliability. Two key characteristics of an ADW are that it is optimized for complex SQL queries and that statistics are gathered as part of DML (Data Manipulation Language) operations. This means that the ADW can handle complicated queries efficiently without manual tuning and it automatically updates statistics during insert, update, and delete operations to ensure query plans are based on up-to-date data distribution.
Other options listed such as creating data summaries, focusing on the creation of indexes, and storing data in row format are not distinctive features of an autonomous data warehouse; in fact, ADWs typically store data in a columnar format, not row format, to enable fast analytical processing.