topic Re: Enqueue / Dequeue in Application Development and Automation Discussions

Enqueue / Dequeue

Former Member — Mon, 21 Jan 2008 11:10:57 GMT

how to use Enqueue / Dequeue concept?

Edited by: Suresh Kumar on Jan 21, 2008 12:11 PM

Re: Enqueue / Dequeue

Former Member — Mon, 21 Jan 2008 11:13:18 GMT

Hi,

Below is the sample code :

call function 'ENQUEUE_E_TABLE'

exporting

tabname = p_table

exceptions

foreign_lock = 1

system_failure = 2

others = 3.

When you are trying to enque it, if you get exception, it means it is

locked by another user.

Thanks,

Sriram Ponna.

Re: Enqueue / Dequeue

Former Member — Mon, 21 Jan 2008 11:14:10 GMT

Lock object concept lock the partcular data record while updating.

decativating lock - Dequeue

When you create lock object in se11 ( Starting EZ if it is custom lock object) and it will create two function module.

enqueue_ezname ,dequeue_ezname..

check in se11 transaction with etable for database table lock.

These function module will not update the data for NAST Table,

Look for NACE Transaction and it is buitt for NAST Table

Reward Points if it is helpful

Re: Enqueue / Dequeue

Former Member — Mon, 21 Jan 2008 11:14:52 GMT

Check this link for Lock fundamentals in SAP:

http://www.saptechies.com/fundamentals-of-enqueue-processing-in-sap-systems/

Example code:

http://help.sap.com/saphelp_nw70/helpdata/en/41/7af4c8a79e11d1950f0000e82de14a/content.htm

Re: Enqueue / Dequeue

Former Member — Mon, 21 Jan 2008 11:16:27 GMT

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..