Oracle audit: Only 'SESSION REC' in ACTION_NAME column
This means you set AUDIT .. BY SESSION instead of AUDIT .. BY ACCESS. When you use BY SESSION, the ACTION_NAME contains SESSION REC, and the actual actions performed by that session are stored in the SES_ACTIONS column as characters. For example the value ---------S------ means there was a select on the object, as each character represents the following actions in order:

ALTER, AUDIT, COMMENT, DELETE, GRANT, INDEX, INSERT, LOCK, RENAME, SELECT, UPDATE, REFERENCES, and EXECUTE

http://docs.oracle.com/cd/B10501_01/server.920/a96536/ch2205.htm#1307791