When an HADB node is started, it will allocate:
Several shared memory segments of fixed size
Internal data structures of fixed size
If an HADB node runs out of resources it will delay and/or abort transactions. Resource usage information is shipped between mirror nodes, so that a node can delay or abort an operation which is likely to fail on its mirror node.
Transactions that are delayed repeatedly may time out and return an error message to the client. If they do not time out, the situation will be visible to the client only as decreased performance during the periods in which the system is short on resources.
These problems frequently occur in “High Load” situations. For details, see High Load Problems