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Do I have to use lock when I am reading data from a table

Former Member
0 Kudos

Hi,

When i am reading data from a table , do I have to set a lock on that table .

Is it necessary for us to set the lock on a table when I am reading data from the table.

When I am updating the table , do I have to set a lock on the table ?

If yes, then what sort of lock-read lock,write lock or shared lock?

Regards,

Sushanth H.S.

3 REPLIES 3

Former Member
0 Kudos

check it out,

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.

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

Reward if helpful

Former Member
0 Kudos

Hi,

My question has not been answered.

My question is when I am reading data from a table, do I have to set a lock.

Suppose,I am selecting data from a database table,then do I need a lock?

Please could you answer to this.

Regards,

Sushanth H.S.

0 Kudos

Hi,

To only read data from a table you do not need a lock.

You only need a lock if there is the possibility of the record being updated (i.e. the user will have the chance to change the data).

Regards,

Nick