What is Read Lock object and write lock object.

[Former Member]

Hi ,

When i have set read lock in this table then why it is giving permission  for modifying record in this table. 

report  zlockobject_zmara.
  data : itab type table of zmara,
            wa like line of itab.
select * from zmara into corresponding fields of table itab.
loop at  itab into wa.
  call function 'ENQUEUE_EZMARA'
  exporting
    mode_zmara           = 'S'
    mandt                = sy-mandt
    matnr                = wa-matnr
*   X_MATNR              = ' '
*   _SCOPE               = '2'
*   _WAIT                = ' '
*   _COLLECT             = ' '
* EXCEPTIONS
*   FOREIGN_LOCK         = 1
*   SYSTEM_FAILURE       = 2
*   OTHERS               = 3
           .
if sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
endif.
  if  wa-matnr = '000000000000000002'.
  wa-ersda = '20130427'.
  wa-ernam = 'Second Value'.
modify itab from wa.
modify zmara from table itab.
  endif.
endloop.

[Former Member]

Hi ,

When i have set read lock in this table then why it is giving permission  for modifying record in this table. 

report  zlockobject_zmara.
  data : itab type table of zmara,
            wa like line of itab.
select * from zmara into corresponding fields of table itab.
loop at  itab into wa.
  call function 'ENQUEUE_EZMARA'
  exporting
    mode_zmara           = 'S'
    mandt                = sy-mandt
    matnr                = wa-matnr
*   X_MATNR              = ' '
*   _SCOPE               = '2'
*   _WAIT                = ' '
*   _COLLECT             = ' '
* EXCEPTIONS
*   FOREIGN_LOCK         = 1
*   SYSTEM_FAILURE       = 2
*   OTHERS               = 3
           .
if sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
endif.
  if  wa-matnr = '000000000000000002'.
  wa-ersda = '20130427'.
  wa-ernam = 'Second Value'.
modify itab from wa.
modify zmara from table itab.
  endif.
endloop.

[Former Member]

Hi,

check  http://help.sap.com/saphelp_nw70/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm

Lock mode

Defines how to synchronize table record access by several users.

The following modes exist:

Exclusive Lock

The locked data can be read or processed by one user only. A request for another exclusive lock or for a shared lock is rejected.

Shared Lock

Several users can read the same data at the same time, but as soon as a user edits the data, a second user can no longer access this data. Requests for further shared locks are accepted, even if they are issued by different users, but exclusive locks are rejected.

Exclusive but not Cumulative Lock

Exclusive locks can be requested by the same transaction more than once and handled successively, but an exclusive but not cumulative lock can only be requested once by a given

[Former Member]

Hi

In both locked object we can read data at same time but only one user can edit the data.

means there is no difference in both lock.

pls specify.

[Former Member]

For your user it will allow to change once ur changing other user cannot change same record

[RaymondGiuseppi]

The SAP lock concept does NOT lock actually records in database, you can always (try) update records with open-sql or native sql statements. You are only protected versus report that use the same concept to prevent this. Read some documentation  like The SAP Lock Concept (BC-CST-EQ)

So this program is wrongly coded, it should have use an exclusive lock, execute any standard transaction like MM02, and execute SM12 to get an idea of the locks mode used by SAP.

The purpose of "S" shared lock is to allow multiple user to display the record, preventing any other user to "E" exclusively lock the record for update, but it does not allow the current user to update the record.

Regards,

Raymond