The loss or corruption of blocks between instances in a cluster indicates that there may be a problem with the cluster interconnect, the primary means of transporting data between instances in an Oracle RAC environment. The charts on this page –Blocks Lost, Blocks Corrupt, Workload, and Latency – may help indicate the source of any problems with the cluster interconnect.
To open the Corrupt / Lost Blocks page
Click Cluster | Corrupt/Lost Blocks.
Charts on the Corrupt/Lost Blocks page
|Blocks Lost and Blocks Corrupt||
These two charts show the current status of requested block transfers across the cluster interconnect. When there is a problem with the loss or corruption of transferred blocks, you should:
Data is exchanged between Oracle RAC instances when the required blocks are available in the buffer caches of ANY of the participating instances. Only when this data is NOT available in cache does Oracle need to read data from disk.
Workload displays block send rate – the amount of data sent by the instances in response to requests received from other instances in the cluster. This consolidated chart shows the workload for each instance, and allows you to compare the details in the Blocks Lost and Blocks Corrupt charts against the corresponding block send rate.
In an Oracle RAC environment, when a block of data is not found in the local cache of an instance, Oracle first checks the cache of the remaining instances in the cluster before reading the block from disk.
The cluster latency is the time taken to receive a block from another instance in the cluster. This consolidated chart shows the recent cluster latency for each instance, and allows you to compare the details in the Blocks Lost and Blocks Corrupt charts against it.