Extreme response time for SESSION_MANAGER is found when analyzing STAD / ST03 / ST03N records.
It is NOT a problem.
Session Manager, STAD, ST03, ST03N, run time, response time
This is a well-known issue that is described in detail in note 569587.
Here is the essential part of note 569587:
"There is another reason for high response times with the session
manager. This is due to a general limitation in the statistics: the
transaction is determined at the end of a dialog step. Usually the last
dialog step of a transaction saves data and takes quite long.
Additionally the most memory is used in this dialog step.
But the transaction is finished during the dialog step. After the
transaction has finished it might return to the transaction which called
it. This is very often the session manager. As the transaction is
determined at the end of the dialog step all the resources consumed
within this dialog step are counted for the next transaction (here the
session manager). The alternative for this behavior would be to get the
transaction code at the beginning of the transaction. But here the same
problem would occur with the first dialog step of the transaction (those
often take quite long as well due to extensive DB statements which run
at the beginning of a transaction).
This is a general limitation that cannot be worked around. To
distinguish between the erroneous records mentioned in the first part of
this note and those which belong to the end of a note one must take a
close look at the ST03 records and decide whether they are normal or
This is SAP Design. There is no solution for this phenomenon
SAP Note 1679959 can also be referred to.