The restriction on data modification, while a data record is being changed by another user, is to ensure data consistency within an SAP system. This is achieved through the use of enqueue service/lock management mechanism which handles locks in the lock table. This locking concept prevents concurrent access to data records by multiple users which may lead to data inconsistency.
Application Locks and Enqueue
SAP enqueue server administers the lock table by checking if requested locks do not conflict with existing locks before a new lock can be set and entered in the lock table.
Some important lock types in SAP that should be taken into consideration include the following:
- Exclusive lock on a database object is only available to and can only be modified by the transaction that sets the lock. Subsequently requested exclusive or shared locks on the same object are not permitted. The exclusive lock is released at the end of the transaction or by the respective user as long as the database object has not been changed.
- Exclusive but not cumulative: these locks can only be called once from the same transaction and subsequently requested locks by the same transaction will not be permitted.
Unduly held locks can be detrimental to SAP system performance, as they can prevent other users from updating critical transactions on the system. The effect of such a problem can be avoided if the enqueue locks and general health condition of the systems are closely monitored.
Failure to obtain a lock in SAP can result in the termination of important processes on the system which can severely impact business activities.
Lock resources are a finite queue and thus the limits need to be monitored and managed accordingly. These translate to services managed by the SAP ASCS/SCS/ERS (Central Services) which includes enqueue and enqueue replication to ensure highly available lock management.
Traditional SAP Monitoring for Application Locks and Enqueue
Lock operations can be monitored in SAP using SM12 in-built features such as the Enqueue statistics and Top capacity usage.
SAP Enqueue Resources can be monitored through the CCMS Infrastructure using specific monitoring functions and configurations like the MTEs of transaction RZ20.
At OS layer: <sid>adm can monitor enqueue and replication using ensmon utility.
Streamline Application Locks and Enqueue Monitoring with IT-Conductor
IT-Conductor contributes to the overall performance of the systems in your landscape by ensuring highly responsive and reliable service levels.
Unduly held locks can be quickly identified using IT-Conductor monitoring features, thus averting poor system performance.
IT-Conductor allows you to monitor the lock operation in your system and avoid the risk of lock table overflow and excessively held locks.
Important enqueue server parameters such as the lock age, error count, and lock count among others can be easily captured in a graphical form using IT-Conductor.
SAP Hostagent Enqueue monitoring can be easily integrated to show both ABAP (ASCS) and JAVA (SCS) enqueue processes and stats.
Enqueue monitoring functionalities in SAP are intelligently complemented by IT-Conductor through the provision of detailed metrics enabling you to quickly locate performance issues and optimize your applications across a series of related KPIs such as updates/queue/DB locks holding SAP locks.
Application Locks Enqu