Look at this for ur understanding. It may be helpfull for you.
Initial Memory Requirement
You can specify the initial amount of main memory assigned to an internal table object when you define the data type using the following addition:
INITIAL SIZE n
. This size does not belong to the data type of the internal table, and does not affect the type check. You can use the above addition to reserve memory space for n table lines when you declare the table object.
When this initial area is full, the system makes twice as much extra space available up to a limit of 8KB. Further memory areas of 12KB each are then allocated.
You can usually leave it to the system to work out the initial memory requirement. The first time you fill the table, little memory is used. The space occupied, depending on the line width, is 16 <= n<= 100.
It only makes sense to specify a concrete value of nif you can specify a precise number of table entries when you create the table and need to allocate exactly that amount of memory (exception: Appending table lines to ranked lists). This can be particularly important for deep-structured internal tables where the inner table only has a few entries (less than 5, for example).
To avoid excessive memory requests, large values for nare treated as follows: The possible maximum value for n results from 8 kilobyte divided by the row length. If you specify a larger value of n, the system calculates a new value so that ntimes the line width is around 12KB.
TYPES: BEGIN OF line,
column1 TYPE i,
column2 TYPE i,
column3 TYPE i,
END OF LINE.
TYPES itab TYPE SORTED TABLE OF line WITH UNIQUE KEY column1.
The program defines a table type itab. It is a sorted table, with line type of the structure line and a unique key of the component column1.
TYPES vector TYPE HASHED TABLE OF i WITH UNIQUE KEY table_line.
TYPES: BEGIN OF line,
column1 TYPE i,
column2 TYPE i,
column3 TYPE i,
END OF line.
TYPES itab TYPE SORTED TABLE OF line WITH UNIQUE KEY column1.
TYPES: BEGIN OF deepline,
field TYPE c,
table1 TYPE vector,
table2 TYPE itab,
END OF deepline.
TYPES deeptable TYPE STANDARD TABLE OF deepline
WITH DEFAULT KEY.
The program defines a table type vector with type hashed table, the elementary line type i and a unique key of the entire table line. The second table type is the same as in the previous example. The structure deepline contains the internal table as a component. The table type deeptable has the row type deepline. Therefore, the elements of this internal table are themselves internal tables. The key is the default key - in this case the column field. The key is non-unique, since the table is a standard table.
Bluesky
