topic Re: LOCKING HELP in Application Development and Automation Discussions

LOCKING HELP

Former Member — Thu, 01 Mar 2007 10:27:37 GMT

PLZ GIMME A PROG WHICH EXPLAINS D LOCKING TECHNIQUE USED IN ABAP

PLZ ALSO PROVIDE A DETAILED EXPLANATION.

Re: LOCKING HELP

Former Member — Thu, 01 Mar 2007 10:30:40 GMT

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

Regards,

Sruthi

Re: LOCKING HELP

Former Member — Thu, 01 Mar 2007 10:33:29 GMT

Hi,

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.

Here we are locking vbeln field in vabk table by using FM

'ENQUEUE_EZLOCK3.

Re: LOCKING HELP

Former Member — Thu, 01 Mar 2007 10:34:48 GMT

Hi ,

Adding to the above answer we can even lock tables also.that is lock can b applied to fields r tables.

Re: LOCKING HELP

Former Member — Thu, 01 Mar 2007 10:35:33 GMT

Assume that you are trying to update a sales order through a transaction.

At the same time, if somebody else is also trying to update the same Order, then it may lead to inconsistensies or deadlock situations. To avoid such situations, we use the locking mechanism.

IN pretty simple words, we lock the ORDER which we are editing and avoid all other users from editing the same Order. we will not unlock it until we finish out updating.

To create our own locks, you should create a LOCK OBJECT in SE11 transaction.

Creating a lock objectt would give your two function modules , one for locking and the other for unlocking.

in your program , this must be the skeleton.

call function 'ENQUE<your lock objectname'

do all the updates

call function 'DEQUE<your lock objectname'

Regards,

Ravi