SAP Lock的一些东西

iyth888

　　SAP Lock Machanism: is to prevent two transactions from changing the same data on the database simultaneously.
　　一些术语:
Lock Entry: is a specific instance of a lock object, which defined in Data Dictionary, and locks a certain database object such as a correction entry or a table entry.lock entries are usually set and deleted automatically when user programs access a data object and release it again.

Lock Modes: S (Shared), E (Exclusive), X (eXclusive non-cumulative), O (Optimistic)
SAP Transaction vs. DB Transaction
Database LUW vs.SAP LUW
Relationship Between SAP Locks and Database Locks
Lock Table
Update Request
　　引用:
SAP Lock basic concept and example
http://help.sap.com/saphelp_nw2004s/helpdata/en/41/7af4c5a79e11d1950f0000e82de14a/frameset.htm
SAP Lock Mechanism Detail
http://help.sap.com/saphelp_nw2004s/helpdata/en/c2/2d7037ecc92a7ee10000009b38f8cf/frameset.htm
　　https://www.sdn.sap.com/irj/sdn/thread?threadID=445275
https://www.sdn.sap.com/irj/sdn/thread?threadID=342161
　　相关的T-Code:
SM12: Lock Entry List
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