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Restarts are either Cold or Coldwait:
Cold (default) Users can log into the system before transaction recovery processing is complete.
Coldwait Logons are blocked until the transaction recovery processing is complete.
Restarts can be:
• Automatic (cold restart) by the system
• Forced (cold or coldwait restart) by the database administrator
An automatic restart is triggered by any of the following:
• A failure on the client (host) system
• A failure within a TDP
• One or more vprocs fail and automatically restart as a result of any the following:
• A software error or vdisk failure
• Database, application, or BYNET software error in a single vproc
• Two physical disks fail in the same rank
• Power surge after a power loss.
• A hardware component fails.
In most cases, Teradata RDBMS restart processing occurs automatically. Users logged on at the time of an automatic restart are informed of the occurrence.
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The type of information returned depends on whether the restart was caused by the failure of a hardware component or by the failure of client, TDP, node, or vproc software.
The impact on your Teradata RDBMS depends on the failed component, as explained in the following tables.
IF the failed component is a ... THEN .
BYNET processing resumes on the other BYNET. Performance may be impacted to some extent. Note: BYNET-initiated restarts never cause a dump.
Disk data may be lost. Tables with fallback continue to be 100% available. Tables without fallback are partially available. Replace disk drive and check table integrity (for detailed instructions, see "Moving Vprocs and Data Rows for Hardware Upgrades" on page A-15). If data needs to be recovered, see "Restoring After a Down AMP" on page 8-34 and "Startup and Recovery" on page 9-8.
Node the impact on performance is minor, if the system is configured with cliques. The other AMPs in the clique take over the responsibilities of the failed node and the system continues. To replace the physical node, see "Moving Vprocs and Data Rows for Hardware Upgrades" on page A-15.
If a disk array loses electrical power but the Teradata RDBMS nodes do not, the following occurs:
Stage Process on an MPP System
1 The AWS notifies the TPA nodes of the disk array event.
2 Teradata RDBMS maps the affected devices to the affiliated vprocs that were marked fatal.
3 Teradata RDBMS issues a TPA reset and comes back up without the vprocs that were marked fatal.
4 Teradata RDBMS notifies the AWS that it has finished handling the event.
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IF the failed component is a ... THEN the impact is .
PE vproc very little on system performance. The maximum session capacity is reduced, and logons may take longer.
AMP vproc the system can continue servicing users with other AMPs, if a single AMP fails in one or more clusters. However, the performance level and response time slows down. If two or more AMPs fail in a single cluster, the system halts. All processing stops until you bring at least one of the AMPs back online. For more information, see "Restoring After a Down AMP" on page 8-34.
For database errors, by default there is always a dump on all nodes. (For types of dumps and how to save them, see "Handling Teradata Crashdumps" on page 10-1.)
UNIX System Resets
On a UNIX systems running the Teradata RDBMS, the following types of resets can occur:
Reset Type Description
UNIX panic The node resets, causing the database to reset also.
Database restart or Trusted Parallel Application (TPA) reset All tasks for vprocs are killed and restarted across all nodes in the Teradata RDBMS configuration. UNIX does not reset. Not all processes are killed. Many of the UNIX processes that create the TPA are cancelled and restarted. Most of the kernel daemons are not killed, and several other processes survive resets.
This section contains instructions for forced restarts of the Teradata RDBMS on either a UNIX or Windows 2000 system. It also contains information for system restarts common to these operating systems.
Warning: On UNIX, the first step is to run the xctl utility to turn on the DBS Start flag. You must do this first in order for Teradata RDBMS to recover correctly.
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After you set the DBS Start flag on, you can force a restart manually by entering the command restart tpa. If possible, wait until no production processing or utility operations are active.
You should only need to force a restart for the following reasons: