Oracle Applications products, and which may also be used with third-party products.
The COMMON_TOP/admin directory is the default location for the concurrent manager log
and output directories. When the concurrent managers run Oracle Applications reports, they
write the log files and temporary files to the log subdirectory of the admin directory
(COMMON_TOP/admin/log) and the output files to the out subdirectory of the admin
By default, the top-level directories for both Java (JAVA_TOP) and HTML (OAH_TOP) are
both under COMMON_TOP.
IAS_TOP is top files/directory under ORA_TOP/iAS I hope it might be clear to you now if not donot worry it will be more clear once you start working as Apps DBA.
Oracle Applications File System - Database Tier
Two other top-level directories store files related to the Oracle Applications database: