If internode communication (INC) fails or the coordinator fails or is shut down during a writer-initiated global transaction, transactions suspend and resume automatically if the INC is restored before a user-specified timeout expires.
Delays in command execution may indicate INC suspend and resume operations. If INC is interrupted, the coordinator suspends a global transaction for an hour. The transaction resumes successfully as soon as INC is restored. If the timeout value elapses, the transaction fails. Set the MPX_LIVENESS_TIMEOUT database option to change the timeout period.
The following cases describe the behavior of writer nodes.
Writer Command Status | Command Behavior | Result |
---|---|---|
Actively executing command | Command suspends, except for ROLLBACK, which executes locally on writer. | Command succeeds. |
New DML command | Command suspends and resumes, except for ROLLBACK and ROLLBACK TO SAVEPOINT, which execute locally on the writer. | If communication is restored, resumed commands succeed. |
Writer Command Status | Command Behavior | Result |
---|---|---|
Suspended DML command on connection | The suspended command fails and returns an error about the non-recoverable state of the transaction. | You must roll back the transaction. Rollback happens automatically if the suspended command is COMMIT or ROLLBACK to SAVEPOINT. |
No suspended DML command on connection | The next command returns an error about the non-recoverable state of the transaction. | You must roll back the transaction. |
To check connection status, use the sp_iqconnection system procedure on a writer node or the sp_iqmpxsuspendedconninfo system procedure on a coordinator.
Run sp_iqmpxincstatistics for a snapshot of the aggregate statistics of the INC status since server startup.