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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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Teradata RDBMS provides several tools with which you can control these elements. The most commonly used are introduced in the following table.

12 - 16 Teradata RDBMS Database Administration

Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

IF you want to . THEN use one or more of these tools . For details and instructions, see .
control logon access User identifiers (name, password, account identifier(s), user group(s), profile) Host group IDs, to authorize logons from specific client platforms with GRANT/REVOKE LOGON ... host_groupid TDQM, to control access to objects as well as active sessions by user, account, performance group, and users within performance group "Controlling System Access" on page 6-17 "Scheduling Workloads with Teradata Dynamic Query Manager (TDQM)" on page 15-12 "GRANT LOGON" in Teradata RDBMS SQL Reference, Volume 6 Teradata Dynamic Query Manager User Guide Teradata Dynamic Query Manager Administrator Guide "LOGON Control" in Teradata RDBMS Security Administration Teradata Director Program Reference
control object access User spool space, to limit response sizes User, role, and / or object access privileges with GRANT/REVOKE Implement operations so that users access portions of data through views, macros, and stored procedures TDQM, to: - Control access to database objects - Limit parameters (such as response rows) based on query type - Limit the number of active queries by user, account, performance group, and users with a performance group Chapter 6: "Controlling Access" "GRANT" statement in Teradata RDBMS SQL Reference, Volume 6 In Teradata RDBMS Security Administration, the sections: - "Access Rights" - "BEGIN LOGGING" Teradata Director Program Reference

12 - 16

Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

IF you want to . THEN use one or more of these tools . For details and instructions, see .
set up automatic job scheduling Priority Scheduler Administrator (PSA) to schedule priority of account access to resources such as CPU and memory TDQM, based on concurrent sessions, query type, account priority, quantity of response rows, and/or workload flow "Managing Resources with Priority Scheduler" on page 15-9 "Scheduling Workloads with Teradata Dynamic Query Manager (TDQM)" on page 15-12 "Priority Scheduler" in Teradata RDBMS Utilities "Priority Scheduler Administrator" in online help for Teradata Manager ACCOUNT keyword under "CREATE USER" in Teradata RDBMS SQL Reference, Volume 4 Teradata Dynamic Query Manager Administrator Guide
justify an upgrade or expansion of your Teradata RDBMS Baseline profiling comparisons Resource Check Tools ResUsage reports "Monitoring Lock Contentions with Locking Logger" on page 12-16 "Solving Bottlenecks by Expanding Your Teradata RDBMS Configuration" on page 12-28 "Using the Resource Check Tools" on page 12-21 Teradata RDBMS Resource Usage Macros and Tables Teradata RDBMS Performance Optimization

Ensuring Node Parallel Efficiency

Node parallel efficiency is not a matter of heaviness of workload; it is a measure of how evenly the workload is shared among the nodes. The more evenly the nodes are shared, the higher the parallel efficiency.

Node parallel efficiency is calculated by dividing average node utilization by maximum node utilization. The result illustrates your node workload distribution, as follows:

12 - 16 Teradata RDBMS Database Administration

Chapter 12: Troubleshooting

Preventing Slowdown or Hang Events

IF node parallel efficiency . THEN .
is nearly 100% the better the nodes are working together.
falls significantly below 100% in that time period, one or a few nodes are working harder than the others.
falls below 60% more often than a couple of sampling periods your installation is not taking advantage of the parallel architecture.

Possible causes of poor parallel node efficiency include:

Down node

Non-Teradata application running on a TPA node

Co-existence system with nodes operating at different speeds

Uneven number of AMPs per node

Two or more AMPs down in one clique

AMP vprocs always run in parallel, but the way data rows are striped across the disks affect the parallel operation of AMP step processing.

Unbalanced, or skewed or spiked, disk loads can cause one or a few AMPs to be doing most of the I/Os. For example, when a numeric column allows zeros and/or nulls, the majority of rows might hash to the same AMP.

If your disk loads are poorly balanced, discuss with operations ways to correct the situation. For example:

Perhaps queries or views against a column with zero/null values could use "WHERE NOT NULL" or "NOT= 0" qualifiers.

If the cause is a non-unique primary index, consider redefining the index, especially for a very large table, to achieve a higher percentage of uniqueness.
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