Hello Suhas,
Here is an example below, where I call a BAPI and also update a Z test table ( the table has only field - counter ). The Update module updates 5 records at a time. In the below example, we create a transaction, which invovles calling a BAPI and a sub transaction which updates 5 table entries.
When the Parent transaction is complete, both the BAPI as well as the Table updates are completed. This is just a basic scenario, there could be other complicated scenario's too.
I had written a response some time back for selective transaction control.However, I had tried with persistent objects back then.
http://scn.sap.com/thread/3317699
Similarly we could create as many dependencies and as many transaction objects as we wish. That's why I had mentioned that the transaction service is just a "wrapper", which gives a lot of
flexibility.
Hope this helps 
. Here is the code snippet.
TYPE-POOLS : oscon.
DATA : lr_tr_mgr TYPE REF TO if_os_transaction_manager,
lr_trans TYPE REF TO if_os_transaction,
lr_trans_sub TYPE REF TO if_os_transaction,
l_tabix TYPE sy-tabix,
lt_table TYPE STANDARD TABLE OF ztest_table,
lr_excpn TYPE REF TO cx_os_transaction.
FIELD-SYMBOLS : <fs_table> TYPE ztest_table.
DATA: w_header TYPE bapi2017_gm_head_01,
w_code TYPE bapi2017_gm_code,
it_item TYPE TABLE OF bapi2017_gm_item_create,
wa_item TYPE bapi2017_gm_item_create,
it_return TYPE TABLE OF bapiret2,
wa_return TYPE bapiret2,
w_head TYPE bapi2017_gm_head_ret,
w_matdoc TYPE bapi2017_gm_head_ret-mat_doc,
w_matyear TYPE bapi2017_gm_head_ret-doc_year.
INITIALIZATION.
cl_os_system=>init_and_set_modes( i_external_commit = oscon_false " No Explicit Commit work, End method triggers it.
i_update_mode = oscon_dmode_update_task )." oscon_dmode_update_task_sync -->COMMIT WORK AND WAIT
"OSCON_DMODE_UPDATE_TASK - > in update task.START-OF-SELECTION.
lr_tr_mgr = cl_os_system=>get_transaction_manager( ).
TRY.
*Parent transaction.
lr_trans = lr_tr_mgr->create_transaction( ).
lr_trans->start( ).l_tabix = sy-tabix.
* l_create = 'X'.
REFRESH it_item.
w_code = '03'.w_header-pstng_date = w_header-doc_date = sy-datum.
w_header-pr_uname = sy-uname.
w_header-ver_gr_gi_slip = '3'.wa_item-material = XXXX.
wa_item-plant = 'XXXX.
wa_item-stge_loc = 'XXXX'.
wa_item-move_type = 'XXXX'.
wa_item-entry_qnt = '1.00'.
wa_item-entry_uom = 'EA'.
wa_item-costcenter = 'XXXX'.
wa_item-gr_rcpt = '1XXXX'..APPEND wa_item TO it_item.
CALL FUNCTION 'BAPI_GOODSMVT_CREATE'
EXPORTING
goodsmvt_header = w_header
goodsmvt_code = w_code
IMPORTING
goodsmvt_headret = w_head
materialdocument = w_matdoc
matdocumentyear = w_matyear
TABLES
goodsmvt_item = it_item
return = it_return.lr_trans_sub = lr_tr_mgr->create_transaction( ).
lr_trans_sub->start( ).DO 5 TIMES.
APPEND INITIAL LINE TO lt_table ASSIGNING <fs_table>.
<fs_table>-counter = sy-index + 70. " some random value.
IF sy-index EQ '5'.
CALL FUNCTION 'ZTEST_TABLE_UPDATE' IN UPDATE TASK
TABLES
it_table = lt_table.
lr_trans_sub->end( ).
ENDIF.
ENDDO.
lr_trans->end( ).CATCH cx_os_transaction INTO lr_excpn .
*Error handling...
WRITE: 'Error Occured in transaction processing'.
ENDTRY.
Thanks,
Venkat.