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Measures reported by HanaLockWaitTest

Lock wait event occurs when a user requests for a resource that is already locked by another user, forcing the former to wait until the latter releases the lock. Lock wait events on a database need to be minimal. If a lock is held on a resource for too long a time, all other requests will be denied access to that resource, thereby leading to blocked transactions,causing critical operations to fail. A transaction can be blocked, for example, for the following reasons:

  • A transaction needs to acquire transactional locks (record or table locks),which are currently being held by another transaction.

  • A required network or disk (database or metadata locks) is currently unavailable.

Moreover, if the number of lock waits grows over time, it will consequently increase the length of the pending requests queue; a long request queue may not only cause the unnecessary erosion of valuable server resources, it may also choke the database server, thereby significantly impacting the quality of the user experience with the server. It is therefore imperative that the lock wait events are monitored, and issues related to such events immediately brought to the attention of administrators.

This test auto-discovers the different lock types that exist currently on the target database server. For each lock type, the test reports the rate at which locks of that type were acquired and the average wait time for the locks. In the process, the test promptly alerts administrators to prolonged waiting time for locks and also pinpoints the exact lock types for which requests are waiting too long. With this information, administrators can easily troubleshoot long wait times.

Outputs of the test: One set of results for every lock type on the target database server being monitored.

Descriptor: Lock Type

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
LockWaits Indicates the rate at which a lock of this type was acquired during the last measurement period. Locks/sec

 

AvarageLockWaitTime Indicates the average time for which requests were waiting to acquire a lock of this type during the last measurement period. Seconds

A high average lock wait time may mean sessions are having to wait for a long time to acquire locks on objects.

A high value may indicate one of the following:

  • Too many transactions happening

  • Locked resources not being released properly

  • Locks are being held by long-running operations