Oracle FND key tables , FND_ID_FLEXS, FND_ID_FLEX_SEGMENTS (1)

FND_ID_FLEXS stores registration information about key flexfields.
Each row includes the four–character code that identifies the key
flexfield, the title of the flexfield (by which a user identifies the
flexfield), the name of the combinations table that contains the key
flexfield columns, and the name of the structure defining (MultiFlex)
column for the flexfield (SET_DEFINING_COLUMN_NAME). Each row
also contains values that identify the application that owns the
combination table and the application that owns the key flexfield, a
table–type flag that specifies whether the combinations table is specific
or generic (S or G), whether dynamic inserts are feasible for the flexfield
(Y or N), whether the key flexfield can use ID type value sets, and the
name of the unique ID column in the combinations table. You need one
row for each key flexfield in each application. Oracle Application Object
Library uses this information to generate a compiled key flexfield
definition

FND_ID_FLEX_SEGMENTS stores setup information about key
flexfield segments, as well as the correspondences between application
table columns and the key flexfield segments the columns are used for.
Each row includes a flexfield application identifier, the flexfield code,
which identifies the key flexfield, the structure number
(ID_FLEX_NUM), the value set application identifier, the segment
number (the segment’s sequence in the flexfield window), the name of
the column the segment corresponds to (usually SEGMENTn, where n is
an integer). Each row also includes the segment name, whether security
is enabled for the segment, whether the segment is required, whether
the segment is one of a high, low segment pair, whether the segment is
displayed, whether the segment is enabled (Y or N), type of default
value, display information about the segment such as prompts and
display size, and the value set the segment uses. Each row also includes
a flag for whether the table column is indexed; this value is normally Y.
You need one row for each segment of each structure for each flexfield.
Oracle Application Object Library uses this information to generate a
compiled key flexfield definition to store in the
FND_COMPILED_ID_FLEXS table