Picked Lamport scheme to generate SCNs, lamportscns

Picked Lamport scheme to generate SCNs, lamportscns

Fault symptom:

Database Node 1 fails to open the database instance after it is suspended and restarted. The warning log has no error. There is only one record: Picked Lamport scheme to generate SCNs. Node 2 is normal and the application can be used normally.

Analysis and Processing:

1. Check the warning logs of the database system, including node 1: alert_szm21.log and node 2: alert_szm22.log. No error is reported.

2 node 1 database instance: oradubug dump systemstate 10 oradebug analyze 3, ass109.awk no waiting and deadlock.

3 metlink's understanding and analysis of Picked Lamport scheme to generate SCNs found

Before Lamport 10.1:

After Commit Broadcas 10.2:

Commit should be recommended when the system has the following problems: (Document ID 259454.1)

However, if any of the following conditions exist, there may be a need

Deviate from the default and explicitly set max_commit_propagation_delay = 0.

-The data consistency between the different instances must be guaranteed and

Immediate I. e. if commits must be seen instantaneously on remote instances.

-When rapid inserts (or updates) and immediate queries of the same dataset are

Done from different instances.

-If middle-tier connection pools are being used in tandem with connection load

Balancing to the RAC instances, and the application is arbitrarily selecting

Connection (and hence an instance) for each SQL operation.

-Some packaged applications (e.g. SAP) might recommend setting this parameter

To a specific value (mostly 0), in which case you shoshould follow

Application vendor's recommendations.

On the SCN algorithm, versions earlier than 10.1 are significantly different from those earlier than 10.2. the old version of the algorithm has shortcomings,

Through the above three analyses: it is decided to restart Node 1, or reproduce the problem or solve the problem: After Node 1 is restarted, the instance can be started normally.

 

Conclusion: for this type of problem, no error information is found through various means, and there is a version difference. Restarting can generally solve the problem,

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