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The SAP Lock Concept (BC-CST-EQ)
The SAP system is equipped with a special lock mechanism that synchronizes database access. The purpose of the lock mechanism is to prevent two transactions from changing the same data in the database simultaneously.
Locks are defined generically as "lock objects" in the Data Dictionary. A lock entry is a lock object and locks a particular data object, such as a correction request or a table entry.
Normally, lock entries are set and deleted automatically when programs access and subsequently release data objects.
The ABAP documentation explains the key elements of the lock concept with regard to programming ABAP transactions in The SAP Lock Concept.
The documentation contains the following sections:
SAP Lock Concept describes how SAP locks work. You have to understand the concepts described here in order to use SAP locks when programming applications.
Standalone Enqueue Server contains details of the architecture of the standalone server and how to use it. It is particularly recommended for high availability scenarios. The Application Server Java uses the Java version of the standalone enqueue server in Central Services.
Important Profile Parameters for the Lock Concept provides a list of the profile parameters relevant for the lock concept. You can use these parameters to tailor your system resources to your needs.
Managing Lock Entries describes lock management (transaction SM12), which you use to display, check, and delete lock entries. This may be necessary if the SAP Dispatcher, the operating system, or the network connection fails, and the Dispatcher cannot delete lock entries. In this event, invalid lock entries remain in effect, blocking access to the locked data when you restart the system.
Analyzing and Solving Problems provides information and tips about handling errors.
The following content is not part of SAP product documentation. For more information, see the following disclaimer .