Ignite may show 'DDL or commits' along with other SQL Statements. This means that at the time Ignite collected the information, the database instance didn't have a SQL Statement associated with the current session. The session is likely in one of the following situations.
1) The session was running a command that is not tracked by the database vendor as a traditional statement.
Data Definition Statements (DDL) - e.g. create table statements
2) The session was between SQL statements. When a session is running multiple SQL Statements it may spend time between the statements cleaning up after the last statement or preparing to accept the next one.
Drill into the 'DDL or commits' with Ignite to determine the program and waits associated with this classification. That information will often give a clue as to what is likely occurring.
Oracle SQL run from DBMS_JOB or DBMS_SCHEDULER
There are two Oracle-specific bugs that cause any SQL executed from DBMS_JOB or DBMS_SCHEDULER to show up as 'DDL or commits'
Bug 5928612 - V$SESSION SQL_ADDRESS / SQL_HASH_VALUE not set for DBMS_JOBs
Fixed in 10.2.0.4 and 22.214.171.124
Bug 5140631 - V$SESSION.sql_address not set by DBMS_SCHEDULER
Fixed in 10.2.0.4 and 126.96.36.199