oracle database SESSION

BY SESSION
Specify BY SESSION if you want Oracle Database to write a single record for all SQL statements of the same type issued and operations of the same type executed on the same schema objects in the same session.
Oracle Database can write to an operating system audit file but cannot read it to detect whether an entry has already been written for a particular operation. Therefore, if you are using an operating system file for the audit trail (that is, the AUDIT_FILE_DEST initialization parameter is set to OS), then the database may write multiple records to the audit trail file even if you specify BY SESSION.
BY ACCESS
Specify BY ACCESS if you want Oracle Database to write one record for each audited statement and operation.
If you specify statement options or system privileges that audit data definition language (DDL) statements, then the database automatically audits by access regardless of whether you specify the BY SESSION clause or BY ACCESS clause.
For statement options and system privileges that audit SQL statements other than DDL, you can specify either BY SESSION or BY ACCESS. BY SESSION is the default.
WHENEVER [NOT] SUCCESSFUL
Specify WHENEVER SUCCESSFUL to audit only SQL statements and operations that succeed.
Specify WHENEVER NOT SUCCESSFUL to audit only statements and operations that fail or result in errors.
If you omit this clause, then Oracle Database performs the audit regardless of success or failure.