Regarding Lock objects concept

[Former Member]

Hi,

I am interested in knowing what is the significance of Lock objects in SAP.

Can we co-relate SAP lock objects with Oracle.

Frnds, I dont need any material i hav enough but i want to know the cocept behind this.

Thanking u all.

regards,

suraj

[Former Member]

Hi

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.

You have to use these function module in your program.

check this link for example.

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

tables:vbak.

call function 'ENQUEUE_EZLOCK3'

exporting

mode_vbak = 'E'

mandt = sy-mandt

vbeln = vbak-vbeln

• X_VBELN = ' '

• _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.

Reward points for useful Answers

Regards

Anji

[Former Member]

Hi

Please read the following simple example

<b>What is Locking ?</b>

- When two users simultaneously attempt to access the same data record, this is synchronised by a lock mechanism.

When dialog transactions are programmed, locks are set and released by calling certain function modules. These function modules are generated automatically from the definition of so-called lock objects in the ABAP/4 Dictionary.

To synchronize the access to a table by setting and removing locks, a Lock object has to be defined in the ABAP/4 Dictionary. Activating the lock object automatically creates function modules for setting and removing locks. These function modules must be included when programming interactive transactions.

<b>Lock Mechanism :</b>

To set locks, a lock object must be defined in the ABAP/4 Dictionary. In this lock object, those tables in which data records are to be locked by calling a lock are determined. All tables included in a lock object must be connected to each other via foreign keys. The key fields of the tables in a lock object form the Lock arguments for the tables. The lock arguments are the basis for formulating the logical condition for identifying the records to be locked.

When activating this lock object, two function modulesB with the names ENQUEUE_<Object_name> and DEQUEUE_<Object_name> are generated.

<b>Example :</b>

Problem :

You wish to prevent a user from being able to change the name of a course or the name of the professor with responsibility for the course at a time when another user is editing the course description (which contains this information).

Solution :

The problem described above can be solved by defining a lock object E_UKURS. This is done by defining primary and secondary tables in the lock object. Table UKURS is check table of table UKRSB, so UKURS should be selected as primary table and UKRSB as secondary table of the lock object.

The Lock argument in this case is the field combination FABNR, KRSNR, and SPRAS (i.e Primary Key Combination).

The Lock mode Shared is to be selected here. This allows several users to access the data simultaneously in display mode.

The lock mode in the generated function modules for setting (ENQUEUE_E_UKURS) and releasing (DEQUEUE_E_UKURS) locks is therefore set to shared as default, but can be overridden by calling the function modules.

If the function module ENQUEUE_E_UKURS is called with FABNR = '1' and KRSNR = '3', the record for course 3 in faculty 1 is locked in table UKURS. Furthermore, all the course descriptions for this course are locked in table UKRSB since field SPRAS was not specified when the function module was called. In such cases, the lock is made generically for a field which is not defined.

If the function module DEQUEUE_E_UKURS is now called with FABNR = '1', KRSNR = '3' and SPRAS = 'D', the German course description is unlocked. All other course descriptions remain locked.

Mark if helpful

Regards

Tushar Mundlik

[former_member150733]

Lock objects are created on tables for mainitaining hte consitency of data. Like restricting only one user/transaction to edit/update the database through a transaction.

The lock concept in sap is implemented as logical locks in that the programmer must expicityl call a

Function Module : enque_<i>lockname</i> (REquest to lock full data / part of data according to the parameters passed to this Function Module )

Regards,

Anish Thomas

before he wants to lock a table or some data in the table. and when the need is over he calls a explicit

Function Module : deque_<i>lockname</i> (Release lock)

End of a transaction automatically triggers a release lock.

THis is strictly a programmer induced wasy of locking data (for consistency) and has no relation to physical locks.

Locks can be created in T.code SE11.

[former_member404244]

Hi,

Please go through the below links.

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

http://dev.mysql.com/doc/maxdb/en/c4/812640632cec01e10000000a155106/content.htm

Regards,

Nagaraj

[Former Member]

Hi,

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

Check these links -

Regards,

Priyanka.