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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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To do this, analyze the performance information on AMPs and PEs, including:

System usage

Resource usage across AMPs and PEs

The amount of disk I/O, BYNET traffic, and client I/O that is occurring

Whether congestion or excessive swapping is a problem on any AMP or PE

Often you can satisfy the need for increased capacity or throughput by adding disks, memory, and/or vprocs. If that does not suffice, you can add nodes. In particular, you must add nodes when your system is CPU bound

12 - 28 Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Solving Bottlenecks by Expanding Your Teradata RDBMS Configuration

Adding Disk Arrays

When you add disk arrays, you increase the capacity for disk I/O.

This is helpful both for a DSS environment with a growing database, and for an OLTP environment with increasing concurrent disk I/O.

To determine if the system needs more storage, look at the ResUsageSvpr table for unusual disk activity, such as frequent:

Mini-cylpacks

Defrags

Packdisks

You may need to add more storage capacity to existing nodes when:

Excessive disk activity is impacting performance

Application changes require additional spool space

Database growth requires additional storage

When you add disks, you run utilities to slice and assign them automatically. New vdisks can be assigned to existing AMPs (join procedure) or new AMPs (reconfiguration).

Note: NCR recommends that you increase memory when you add AMPs.

Adding Vprocs

Add vprocs for the following reasons:

IF you want to increase . THEN add .
storage capacity disks, probably with AMPs, and perhaps nodes. When you add storage, you normally add AMPs. The number of AMPs you add depends on the number of ranks assigned to the existing AMPs. For example, if you add two disk cabinets to each of 20 ranks, you would add 10-20 more AMPs to your configuration. If you add AMPs, be sure your memory is adequate. Normally, NCR recommends you add memory when you add AMPs. If your existing CPUs will not be able to handle the load caused by the additional AMPs, you also need to consider adding nodes.

12 - 28 Teradata RDBMS Database Administration

Chapter 12: Troubleshooting

Solving Bottlenecks by Expanding Your Teradata RDBMS Configuration

IF you want to increase . THEN add .
single-user response time AMPs. Optimization of single-user throughput or response time is especially significant when there are fewer AMPs than CPUs per node. In a concurrent workload, you might be able to achieve the desired throughput by adding more AMPs to existing nodes. Be sure your memory is adequate for the additional AMP workload.
capacity for concurrent sessions PEs, perhaps nodes, and perhaps a channel connection. For network sessions, add PEs if you have fewer than 10 PEs per node. If you already have 10 PEs per node, add another node. Note: The session limit is 120 for each PE and 1200 for each gateway. Because each node runs just one instance of the gateway, more than 10 PEs per node will not provide increased network sessions. The channel driver does not have a session limit, but normally one PE is configured for each channel connection. If your configuration has less than 4 channel connections, you can add another channel connection and another PE. Verify that there is enough CPU capacity to handle more PEs. If there is not, add nodes.
When you add memory, you increase the cache to maximize the capability of the CPUs. This is helpful when CPUs are processing faster than the disk contents can be read into memory (that is, the system is I/O-bound). Add more memory for the following conditions:
Condition Description
Add vprocs to existing nodes Each vproc consumes 32 MB of memory. When you add vprocs to existing nodes, you probably should add memory. Additional vprocs can substantially reduce free memory, which can cause more I/Os because the system can cache fewer data blocks.
Excessive paging/ swapping (thrashing) More memory means that more code and data can be cached, achieving less I/O for paging and swapping.

12 - 28 Teradata RDBMS Database Administration Chapter 12: Troubleshooting

Solving Bottlenecks by Expanding Your Teradata RDBMS Configuration

Condition Description
Tables in Increased memory may reduce I/O by accommodating:
memory Tables that are currently too large to remain in memory during
processing
More small tables concurrently residing in memory during
processing
I/Os can be affected by the size of table data blocks. For information,
see the DATABLOCKSIZE option of the CREATE TABLE statement in
Teradata RDBMS SQL Reference, Volume 4.

Adding Nodes

Often you can satisfy the need for increased capacity or throughput by adding disk arrays, memory, and/or vprocs. If that does not suffice, you can add one or more nodes.

Although adding a new node costs more than adding disks and memory to an existing node, you must add nodes when your system is CPU bound.
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