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about lock object and how to create it

Hi ABAP gurus,

Can any one explain about the Lock Objects and How to create Lock object step by step.

Rgds,

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  • Best Answer
    author's profile photo Former Member
    Former Member
    Posted on Apr 23, 2007 at 11:28 AM

    Hi Rangamma,

    Lock Objects are used to synchronize access to the same data by

    more than one user. Function modules that can be used in

    application programs are generated from the definition of a lock

    object in the ABAP Dictionary.

    The R/3 System synchronizes simultaneous access of

    several users to the same data records with a lock

    mechanism. When interactive transactions are programmed,

    locks are set and released by calling function modules .

    These function modules are automatically generated from the

    definition of lock objects in the ABAP Dictionary.

    Structure of a Lock Object

    The tables in which data records should be locked with a

    lock request are defined in a lock object together with their

    key fields.

    When tables are selected, one table (the primary table) is

    first selected. Further tables (secondary tables) can also be

    added using foreign key relationships.

    Lock Arguments

    The lock argument of a table in the lock object consists of the

    key fields of the table.

    The lock argument fields of a lock object are used as input

    parameters in the function modules for setting and removing

    locks generated from the lock object definition. When these

    function modules are called, the table rows to be locked or

    unlocked are specified by defining certain values in these fields.

    These values can also be generic. The lock argument fields

    therefore define which subset of the table rows should be

    locked.

    Data Dictionary/ Lock Objects

    The simplest case of a lock object consists of exactly one

    table and the lock argument of the table is the primary key of

    this table. Several tables can also be included in a lock

    object. A lock request therefore can lock an entire logical

    object, and not only a record of a table. Such a logical object

    can be for example a document comprising an entry in a

    header table and N entries in a positiontable.

    Lock Mode

    The lock mode controls whether several users can access

    data records at the same time. The lock mode can be

    assigned separately for each table in the lock object. When

    the lock is set, the corresponding lock entry is stored in the

    lock table of the system for each table.

    Access by more than one user can be synchronized in the

    following ways:

    Exclusive lock: The locked data can only be displayed or

    edited by a single user. A request for another exclusive lock

    or for a

    shared lock is rejected.

    Shared lock: More than one user can access the locked data

    at the same time in display mode. A request for another

    shared lock is

    accepted, even if it comes from another user. An exclusive lock

    is

    rejected.

    Exclusive but not cumulative: Exclusive locks can be requested

    several times from the same transaction and are processed

    successively. In contrast, exclusive but not cumulative locks

    can be called only once from the same transaction. All other

    lock requests are rejected.

    1> Select object type Lock object in the initial screen of the ABAP

    Dictionary, enter an object name and choose Create.

    The name of a lock object should begin with an E (Enqueue).

    The maintenance screen for lock objects is displayed.

    2> Enter an explanatory short text in the field Short text.

    You can then use the short text to find the lock object at a later

    time, for example with the R/3 Repository Information System.

    3> Enter the name of the primary table of the lock object.

    All other tables in the lock object must be linked with the

    primary table using foreign keys.

    4> Select the lock mode of the primary table in the field below

    it.

    The lock mode is used as the default value for the

    corresponding parameters of the function modules generated

    from the lock object.

    5> Choose Add if you want to lock records in more than one

    table with the lock object.

    A list of all the tables linked with the primary table using valid

    foreign keys is displayed. Select the appropriate table. The lock

    mode of the primary table is copied as lock mode. You can

    change this setting as required, for example you can assign the

    lock mode separately for each table.

    Similarly, you can add a table linked with the secondary table

    just added with foreign keys. To do this, place the cursor on

    the name of the secondary table and choose Add.

    If no lock mode is assigned to a table, no lock is set for the

    entries in this table when the generated function modules are

    called. You should not assign a lock mode if a secondary table

    was only used to define a path between the primary table and

    another secondary table with foreign keys.

    6> Save your entries.

    A dialog box appears in which you have to assign the lock

    object a development class.

    7> You can define whether the function modules generated from

    the lock object should be RFC-enabled on the Attributes tab

    page. If you set the Allow RFC flag, the generated function

    modules can be called from within another system with Remote

    Function Call. If you permit Remote Function Calls for an

    existing lock object, you must ensure that the generated

    function modules are called from within an ABAP program with

    parameters appropriate for the type. You should therefore check

    all programs that use the associated function modules before

    activating the lock object with the new option.

    8> Choose Activate.

    ********Rewards some points.

    Rgds,

    P.Naganjana Reddy

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  • author's profile photo Former Member
    Former Member
    Posted on Apr 23, 2007 at 11:33 AM

    SE11->Enter the Lock Object name(EZ_MAT)->Provide Description/Enter the table name as MARA->Select Exclusive,cumulative->Click on Lock Parameter->here you can see key fields->activate this

    got o SE37->

    You can find 2 FM's which are assined to this.

    DEQUEUE_EZ_MAT Release lock on object EZ_MAT

    ENQUEUE_EZ_MAT Request lock for object EZ_MAT

    Call this in your program/any where to lock/unlock the material (Example)...

    Thanks

    Eswar

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  • Posted on Apr 23, 2007 at 11:29 AM

    lock-objects

    Regards,

    Amit

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  • author's profile photo Former Member
    Former Member
    Posted on Apr 23, 2007 at 11:34 AM

    Hi Rangamma,

    Check this info.

    Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.

    SAP Provide three type of Lock objects.

    - Read Lock(Shared Locked)

    protects read access to an object. The read lock allows other transactions read access but not write access to

    the locked area of the table

    - Write Lock(exclusive lock)

    protects write access to an object. The write lock allows other transactions neither read nor write access to

    the locked area of the table.

    - Enhanced write lock (exclusive lock without cumulating)

    works like a write lock except that the enhanced write lock also protects from further accesses from the

    same transaction.

    You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.

    Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.

    Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.

    Technicaly:

    When you create a lock object System automatically creat two function module.

    1. ENQUEUE_<Lockobject name>. to insert the object in a queue.

    2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.

    Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.

    SAP Provide three type of Lock objects.

    - Read Lock(Shared Locked)

    protects read access to an object. The read lock allows other transactions read access but not write access to

    the locked area of the table

    - Write Lock(exclusive lock)

    protects write access to an object. The write lock allows other transactions neither read nor write access to

    the locked area of the table.

    - Enhanced write lock (exclusive lock without cumulating)

    works like a write lock except that the enhanced write lock also protects from further accesses from the

    same transaction.

    You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.

    Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.

    Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.

    Technically:

    When you create a lock object System automatically creat two function module.

    1. ENQUEUE_<Lockobject name>. to insert the object in a queue.

    2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.

    http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm

    GO TO SE11

    Select the radio button "Lock object"..

    Give the name starts with EZ or EY..

    Example: EYTEST

    Press Create button..

    Give the short description..

    Example: Lock object for table ZTABLE..

    In the tables tab..Give the table name..

    Example: ZTABLE

    Save and generate..

    Your lock object is now created..You can see the LOCK MODULES..

    In the menu ..GOTO -> LOCK MODULES..There you can see the ENQUEUE and DEQUEUE function

    Lock objects:

    http://www.sap-img.com/abap/type-and-uses-of-lock-objects-in-sap.htm

    http://help.sap.com/saphelp_nw04s/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm

    Match Code Objects:

    http://help.sap.com/saphelp_nw2004s/helpdata/en/41/f6b237fec48c67e10000009b38f8cf/content.htm

    http://searchsap.techtarget.com/tip/0,289483,sid21_gci553386,00.html

    See this link:

    http://www.sap-img.com/abap/type-and-uses-of-lock-objects-in-sap.htm

    Hope this resolves your query.

    <b>Reward all the helpful answers.</b>

    Regards

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