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Repeated Read-and-Confirm Cycles Using the LDQ API ("Read")

In the same session several read - read - … - read-confirm-commit cycles can occur. Here is a simplified illustration of the single cycle described in the example before.

Sequence Diagram:

The following outline illustrates n_cycles repetitions of a cycle with n_times reads of n_units units at once, with an explicit commit at the end of each cycle.

Input Parameters

      ap_name           TYPE ldq_application_name DEFAULT 'Perf_TEST',
      qp_name           TYPE ldq_queue_name DEFAULT 'LDQ_TEST_',
      n_queues          TYPE i DEFAULT 5,
      n_units           TYPE i DEFAULT 10,
      n_times           TYPE i DEFAULT 3.
      n_cycles          TYPE i DEFAULT 4.


DATA: l_ldq_reader      TYPE REF TO if_ldq_reader,
      l_ldq_unit_reader TYPE REF TO if_ldq_unit_reader.
DATA: l_queue_name_tab  TYPE ldq_queue_name_tab,
      l_queue_name      TYPE ldq_queue_name.
DATA: l_xdata           TYPE xstring,
      l_cdata           TYPE string.
DATA: l_size            TYPE i.
DATA: l_content_tab     TYPE ldq_unit_content_reader_tab.
DATA: l_state_tab       TYPE ldq_unit_state_reader_tab.

DATA: l_del             TYPE i.
DATA: l_seq_nr          TYPE ldq_unit_id.
DATA: l_queue_nr(4)     TYPE n.
DATA: l_lines           TYPE i.
DATA: l_last_lines      TYPE i.
DATA: l_unit            TYPE i.

DATA: l_state_wa        TYPE REF TO if_ldq_unit_state_reader,
      l_content_wa      TYPE REF TO if_ldq_unit_content_reader.
DATA: l_format          TYPE ldq_data_format.
DATA: l_next_state_nr   TYPE i.
DATA: l_number          TYPE i.
TYPES: BEGIN OF lt_my_unit_reader,
         unit_reader TYPE REF TO if_ldq_unit_reader,
         queue_name    TYPE ldq_queue_name,
      END OF lt_my_unit_reader.
DATA: l_my_unit_reader_tab TYPE TABLE OF lt_my_unit_reader.
DATA: l_my_unit_reader TYPE lt_my_unit_reader.

FIELD-SYMBOLS: <l_content_wa> TYPE REF TO if_ldq_unit_content_reader.
FIELD-SYMBOLS: <l_state_wa>   TYPE REF TO if_ldq_unit_state_reader.

Creation of Queue Names

CLEAR: l_queue_name_tab[], l_content_tab[].
DO n_queues TIMES.
  l_queue_nr = sy-index.
  CONCATENATE qp_name l_queue_nr INTO l_queue_name.
  CONDENSE l_queue_name NO-GAPS.
  APPEND l_queue_name TO l_queue_name_tab.

LOOP AT l_queue_name_tab INTO l_queue_name.

Creation of LDQ Application Object

  l_ldq_reader       = cl_ldq_application=>get_reader( ap_name ).

Creation of LDQ Queue Objects for each Queue Name

  l_my_unit_reader-unit_reader = l_ldq_reader->set_queue_name( l_queue_name ).
  l_my_unit_reader-queue_name  = l_queue_name.
  APPEND l_my_unit_reader TO l_my_unit_reader_tab.

Several read-read-…-read-confirm cycles

DO n_cycles TIMES.


Read the Block Units over all Queues n_times

DO n_times TIMES.

  LOOP AT l_my_unit_reader_tab INTO l_my_unit_reader.

Get n_units in one Block

    l_content_tab = l_my_unit_reader-unit_reader->get_next_contents( n_units ).

    l_unit = LINES( l_content_tab ).

Retrieve contained Information out of Content Object

    CLEAR l_number.
    WRITE: / l_unit, 'Qname:', l_my_unit_reader-queue_name.
    LOOP AT l_content_tab  ASSIGNING <l_content_wa>.
      l_format = <l_content_wa>->get_format( ).
      IF cl_ldq_unit_writer=>co_character_data_type = l_format.
        l_cdata = <l_content_wa>->get_cdata( ).
        l_xdata = <l_content_wa>->get_xdata( ).
      l_seq_nr  = <l_content_wa>->get_sequence_number( ).
      l_size = <l_content_wa>->get_size( ).

      l_number = l_number + 1.
      WRITE: /10 'number:', l_number, 'sequence number =', l_seq_nr, 'size in kb:', l_size.

Confirm Read Units in the Database

    l_my_unit_reader-unit_reader->confirm( ).

Persist the Read Status of LDQ Data into the Database


  ENDLOOP.      next read-read-…-read-confirm cycle

  ENDLOOP.      next queue