table SMODISRC with filed OPERATION value

Hi

can any one please help me,

what is the use of this table SMODISRC with filed OPERATION value

and what is the purpose and the values are

PRE Exit at start of modularization unit

POST Exit at end of modularization unit

ALL Unit overlay

NEW New unit

REPA Modification without support

TRSL Translation entry

IMP Business Add-In - Implementation

MOD Modifications to sources

MIGR Matchcode object migration

NOTE Note Corrections

ORIG Object Reset to Original

TORI Translation Entry Reset to Original

Can any one please help me .