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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 - 14

Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Diagnosing SSO Logon Errors (Windows 2000 only)

• The form of username being submitted does not agree with the form defined as valid by the Append Domain Name field. Two forms are possible, but only one can be in force at a time.

The choices for forms of username are as follows:

IF your site ... THEN the Gateway GDO should be .
does not use domain names (userID is username) Append Domain Name: no
uses domain names (user ID is " username@domainname") Append Domain Name: yes
To enable one form or the other, use the gtwcontrol command as follows:
IF you want to . THEN use gtwcontrol with .
see the current settings of the GTWCONTROLGDO the -d option, as follows: gtwcontrol -d
toggle the value of the Append Domain Name field the -F option, as follows: gtwcontrol -F

12 - 14 Teradata RDBMS Database Administration

Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

Preventing Slowdown or Hang Events

Problem detection includes monitoring transaction processing as well as looking at how often a resource is in use during a given period. This could include asking questions such as:

• Is one query consistently blocking others?

• Are there many transaction deadlocks during peak workloads?

• Are all AMPs working equally hard?

• What are the disk loads and I/O counts?

• Is traffic on the BYNET moving normally?

The following tips are useful in administering your Teradata RDBMS in such a way as to minimize the occurrence of impacted performance.

Monitoring Lock Contentions with Locking Logger

Locking Logger, sometimes called the DumpLock log, is an optional feature. If you enable Locking Logger, each AMP creates a circular memory buffer for saving information about transaction lock contentions.

The utility provides a tool for creating a table that stores data extracted from the buffers. (You cannot access system buffers directly.) Query this table to identify the session or sessions causing a locking queue delay.

When a transaction is blocked due to a lock delay, the AMP writes an entry in its lock log buffer. The entry includes the level of lock being held and the transaction, session, and locked-object identifiers of the involved request. The buffers hold approximately 810 entries per AMP in a circular fashion—when the buffer is full, the next entry overwrites the first, providing a continuously updated log of the last 810 transaction locks encountered by each AMP.

If the same query or group of queries appear consistently in the lock log table, use DBQL and Teradata Visual Explain to analyze them and determine and eliminate the cause. Be sure you have collected current statistics before criticizing the query structure or processing results. You can use the Statistics Wizard to determine what columns to collect statistics on, you can use either or both forms of the COLLECT STATISTICS statement (if you have enabled QCF), and you can use the Index Wizard to analyze the efficiency of indexed access. (For details on analysis tools, see Chapter 13: "Database Analysis".)

The procedure to enable Locking Logger and create the table entails these steps:

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Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

Step Process Action References
1 Enable Locking Logger Run the DBS Control Utility to set the value in the Locking Logger field to TRUE (enabled). "DBS Control Utility" in Teradata RDBMS Utilities
2 Create an accessible log table In an interactive window, enter the START DUMPLOCKLOG command. You can use: • From an AWS console, the Supervisor window of the Database Window tool. • From a Windows 2000 console, either Tera-data Manager, or the Database Window, Teradata Command Prompt, or Teradata Multitool interactive windows. • Teradata Manager User Guide • Teradata Manager online help • "Locking Logger Utility" in Teradata RDBMS Utilities, especially the sections: - "Starting Locking Logger" - "Lock Log Tables"
3 Specify what data you want extracted from the buffers and stored in the table • Using Teradata Manager, select either: - A snapshot of the current buffer entries - "Continuous" for add-on entries • Using DUMPLOCKLOG, respond to each prompt as appropriate. • Teradata Manager User Guide • Teradata Manager online help • "Lock Log Tables" under "Locking Logger Utility" in Teradata RDBMS Utilities
4 Retrieve or report logged data Do any of the following: • Query the Lock Log table directly • Generate reports using BTEQ or Teradata Manager • Basic Teradata Query Reference • Teradata Manager User Guide • Teradata Manager online help

Controlling Session Elements

All database systems reach saturation from time to time, particularly in ad-hoc query environments. However, on Teradata RDBMS you can control session elements such as user spool space and job entry, and thus you can minimize how often end-users might saturate the database capabilities.
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