topic Re: Lock Objects in Application Development and Automation Discussions

Lock Objects

Former Member — Tue, 03 Jun 2008 19:31:05 GMT

Hi,

I am doing Record Level Locking ,

I am using some function modules.

But i ve one doubt ,What is Lock Objects?

Regards,

Kalidas

Re: Lock Objects

Former Member — Tue, 03 Jun 2008 19:34:13 GMT

if u want to know indepth go to

http://abapprogramming.blogspot.com/2007/11/match-code-objects-in-abap-2.html

lock objects used to synchornize access of several users using same data.

Lock Object is a relationship defined in the Data Dictionary between a main table and possible secondary tables

*******

Lock object is a virtual link of several SAP tables which

is used to synchronize simultaneous access by two users to

the same set of data (SAP lock concept).

[or]

when two users simultaneously attempt to access the

same data record, this is cynchronised by a lock mechanism.

To set the locks,

you must define a lock object in ABAP dictionary. The name

of lock object should start with 'E'.

Thd Fun Modules for requesting and releasing lock which are

create automatically when the lock object is activated must

be linked to the programming of the relevant online

transactions.

They are 3 types:

1) write (exclusive lock)

2) read ( shared lock )

3) exclusive but not cummulative

Re: Lock Objects

Former Member — Tue, 03 Jun 2008 19:35:22 GMT

Hello,

See this: [https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/c1be1003-0701-0010-3795-f87160de6483] at page 21.

Regards.

Re: Lock Objects

Former Member — Tue, 03 Jun 2008 19:36:28 GMT

Hi,

Lock object are use in SAP to avoid the inconsistancy at the time of data is being insert or modify into the database.

in SAP we have 3 lock objects

1)Read Lock

2)Write Lock

3)Enhanced write Lock

To create Lock object use T-Code SE11

when u create lock object system automatically creates 2 Function Modules

ENQUEUE_LOCKOBJECT NAME

DEQUEUE_LOCKOBJECT NAME

ENQUEUE_LOCKOBJECT NAME : To insert the object in a queue

DEQUEUE_LOCKOBJECT NAME :To remove the object.

Thanks

Prashanth

Re: Lock Objects

Former Member — Tue, 08 Jul 2008 07:07:51 GMT

Hi Kalidas,

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.

Normally ABAPers will create the Lock objects, because we know when to lock and how to lock and where to lock the Object then after completing our updations we unlock the Objects in the Tables

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

purpose: If multiple user try to access a database object, inconsistency may occer. To avoid that inconsistency and to let multiple user give the accessibility of the database objects the locking mechanism is used.

Steps: first we create a loc object in se11 . Suppose for a table mara. It will create two functional module.:

1. enque_lockobject

1. deque_lockobject

before updating any table first we lock the table by calling enque_lockobject fm and then after updating we release the lock by deque_lockobject.

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..