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Teradata RDBMS Database Administration - NCR

NCR Teradata RDBMS Database Administration - NCR , 2004. - 616 p.
Download (direct link): teradatadatabaseadmin2004.pdf
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12 - 16

Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

Using the Resource Check Tools

Although the set of utilities in Resource Check Tools (RCT) is useful for identifying a slowdown or hang, you also can use them periodically to expose a potential problem before it impacts production.

The process is as follows:

Step

Action

References

After Teradata RDBMS is installed, determine what is a reasonable response interval for the RDBMS. Use this as the parameter to dbschk.

Using the response interval you determined in step 1, run dbschk as a background task to continually monitor the response.

Note: Run dbschk only when DBS logons are enabled (system status is: *Logons-Enable*).

To turn dbschck... Use the following command.
ON dbschk -power 1
OFF dbschk -power 0

"Resource Check Tools" in Teradata RDBMS Utilities

At the UNIX command prompt:

man dbschk

man syscheck

At the DOS command prompt:

pdehelp dbschk

pdehelp

syscheck

Look at your site-specific copy of the syscheckrc file to see whether a value is set at a dangerous low for a resource, such as UNIX free memory, free swap space, or AMP worker tasks. For example, the node-only section of syscheckrc would include the following:

1

2

3

Resource value Comment
Free memory Below 1000 could be a warning level.
PDE Msg Daemon Queue Length Above 100 msg counts implies congested state.
BNS Blocked Queue Length Above 200 msg implies congested state.
Available AMP worker task Below 2 implies available AMP worker tasks are running low.
BNS Msg Reject % Above 80% implies congested state.

Note: Congested means that the local node (or system-wide) is very busy and heavily loaded.

12 - 16 Teradata RDBMS Database Administration

Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

Step

Action

References

Create a site-specific file by doing one of the following:

Either copy the default file to a location as indicated below

Or use the nodecheck utility with the following options:

- First use the -D option (to redirect output and create an rscfilename that you can customize)

- Then use the -r rscfilename option to read the created file

A variation of syscheckrc resides on each node, as follows:

File Description Location
Default syscheckrc: Should not be modified Is the resource file for nodecheck and syscheck. On UNIX: / usr/ntos/etc On Windows 2000: Program Files\NCR\TDAT\LPDE\etc
Your site-specific copy can be modified for your site to specify: WARN and ALERT levels for each system resource Sample number and sleep time. On UNIX: /ntos On Windows 2000: Program Files\NCR\TDAT\tdConfig

"Resource Check Tools" in Teradata RDBMS Utilities

At the UNIX command prompt: man dbschk man syscheck At the DOS command prompt:

pdehelp dbschk

pdehelp

syscheck

If you see a LOGEVENT generated by dbschk in the stream log, which indicates that the response from RDBMS exceeded the interval specified as reasonable, you should:

a Consult with daily operations to find out why the slowdown or hang occurred.

b If operations cannot explain the event, go to step 5.

Run the syscheck utility to see if any of the resources defined in syscheckrc are at the WARN level.

4

5

6

12 - 16

Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Troubleshooting a Slow or Hung Job

Troubleshooting a Slow or Hung Job

If Teradata RDBMS slows down or hangs unexpectedly, perform your troubleshooting in the following order:

Step Check for . Because . For more information, see .
1 down hardware A down BYNET, AMP, or PE can cause your job to appear hung or to run slowly. A down AWS or bad UPS can reset the Battery Status field of PDE Control GDO to Not Present, so that Teradata RDBMS writes in safe mode. Safe mode uses many I/Os and can slow throughput. To fix temporarily, run the ctl utility (on Windows 2000) or xctl utility (on UNIX) and reset the Battery Status field to AutoDetect. Note: These are important troubleshooting steps. Teradata Manager User Guide Teradata RDBMS Database Window Teradata RDBMS Utilities
2 busy system this is also part of ruling out a hardware problem; for example, it may be time for expansion. Investigating a busy system also involves determining: The resource bottleneck (AMP CPU, disk) Who is using the bottlenecked resource and by what amount Size of spool file Data distribution across the AMPs
3 blocked job Host utility (HUT) locks remaining from ARC operations must be released manually with the RELEASE LOCKS command. A long-running job holding an exclusive or write lock on a popular object must be aborted manually. You can use the ABORT SESSION command of Teradata Performance Monitor from Teradata Manager via MONITOR. "RELEASE LOCK Statement" on page 8-33 "ABORT SESSION Command" on page D-9
Previous << 1 .. 147 148 149 150 151 152 < 153 > 154 155 156 157 158 159 .. 218 >> Next