what is difference between Shared ,Exclusive and Exclusive but not commulat

[Former Member]

what is difference between Shared ,Exclusive and Exclusive but not commulative lock modes plese tell me

[Former Member]

Check this link -

It explains locking in detail.

http://help.sap.com/saphelp_nw04/helpdata/en/c2/2d7037ecc92a7ee10000009b38f8cf/frameset.htm

[former_member223537]

<b>Exclusive lock</b>

The locked data can be read or processed by one user only. A request for another exclusive lock or for a shared lock is rejected.

<b>Shared lock</b>

Several users can read the same data at the same time, but as soon as a user edits the data, a second user can no longer access this data. Requests for further shared locks are accepted, even if they are issued by different users, but exclusive locks are rejected.

<b>Exclusive but not cumulative lock</b>

Exclusive locks can be requested by the same transaction more than once and handled successively, but an exclusive but not cumulative lock can only be requested once by a given transaction. All other lock requests are rejected.

[Former Member]

Lock objects are used to synchronize access to the same data by more than one program.

The lock mode controls whether several users can access data records at the same time. The lock mode can be assigned separately for each table in the lock object. When the lock is set, the corresponding lock entry is stored in the lock table of the system for each table.

There are three types of lock modes

1.Exclusive

2.Shared

3.Exclusive not cummulative

Exclusive lock: The locked data can only be displayed or edited by a single user. A request for another exclusive lock or for a shared lock is rejected.

Shared lock: More than one user can access the locked data at the same time in display mode. A request for another shared lock is accepted, even if it comes from another user. An exclusive lock is rejected.

Exclusive but not cumulative: Exclusive locks can be requested several times from the same transaction and are processed successively. In contrast, exclusive but not cumulative locks can be called only once from the same transaction. All other lock requests are rejected.

please go through these links:

http://help.sap.com/saphelp_nw04/helpdata/en/a2/3547360f2ea61fe10000009b38f839/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/af/22ab01dd0b11d1952000a0c929b3c3/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eeb2446011d189700000e8322d00/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eebf446011d189700000e8322d00/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eed9446011d189700000e8322d00/frameset.htm

briefly :

You can lock the table or record by using following types of locking:

1) Exclusive (E) the locked data can only be displayed or modified by single user i.e the owner of the object. Access to other users is denied.

2) Shared (S) several users can access the same record simultaneously, but only in display mode and except the first one, who has asked for the data in update mode.

3) Exclusive not cumulating (X) it is similar to exclusive lock. It allows only a single user access. E can be called several times from the same transaction. In contrast, a lock type X can be called only once during the transaction. Any other call for this lock is rejected.

Activation of Lock Object

1) When you activate the lock object, the functions are automatically generated. And these are ENQUEUE-EZN and DEQUEUE-EZN. EZN is name of the lock object.

2) While ENQUEUE is used in program to set the code over the selected data depending upon the lock object arguments. DEQUEUE is used to release the lock.

Thanks

Seshu

[Former Member]

pls go thrugh this

<a href="http://help.sap.com/saphelp_nw04s/helpdata/en/7b/f9813712f7434be10000009b38f8cf/frameset.htm">http://help.sap.com/saphelp_nw04s/helpdata/en/7b/f9813712f7434be10000009b38f8cf/frameset.htm</a>

regards

shiba dutta

[Former Member]

Shared means for all users who are using that program

Exclusive means only for that user (single user)

Lock mode

Defines how to synchronize table record access by several users

Exclusive lock or read lock

The locked data can be read or processed by one user only. A request for another exclusive lock or for a shared lock is rejected.

Shared lock or write lock

Several users can read the same data at the same time, but as soon as a user edits the data, a second user can no longer access this data. Requests for further shared locks are accepted, even if they are issued by different users, but exclusive locks are rejected.

Exclusive but not cumulative lock

Exclusive locks can be requested by the same transaction more than once and handled successively, but an exclusive but not cumulative lock can only be requested once by a given transaction. All other lock requests are rejected

check

http://help.sap.com/saphelp_40b/helpdata/en/cf/21eea5446011d189700000e8322d00/content.htm

http://help.sap.com/saphelp_nw04s/helpdata/en/a2/3547360f2ea61fe10000009b38f839/frameset.htm

Rewards if useful.................

Minal