Load Balancing - OLE DB Provider for Teradata

OLE DB Provider for Teradata User Guide
Product
OLE DB Provider for Teradata
Release Number
15.00
Language
English (United States)
Last Update
2018-09-28
dita:id
B035-2498
Product Category
Teradata Tools and Utilities

Load Balancing

Load balancing is an attempt to distribute connections among all the COPs of a Teradata server, rather than only using COP 1.

The basic scheme is:

  • If the data source is a specific IP address, then OLE DB Provider for Teradata will only use that address for a connection. Both IPv6 and IPv4 addresses are supported.
  • If the data source is a specific COP, for example vadorcop1, OLE DB Provider for Teradata will only try to connect to that COP. However, all of the IP addresses defined for that COP (both IPv6 and IPv4) will be queried and all of those addresses will be used if necessary to connect to the COP.
  • If the data source is the name of a Teradata server, then OLE DB Provider for Teradata's actions are based on the setting of the NumberOfCOPs attribute:
    •  

    Table 20: Load Balancing 

    IF the...

    then...

    NumberOfCOPs is not set

    OLE DB Provider for Teradata attempts to connect to the data source name, and if necessary, the server's first COP.

    All of the known IP addresses (both IPv6 and IPv4) for those two are used in trying to make a connection.

    NumberOfCOPs > 0

    OLE DB Provider for Teradata chooses a COP at random on the first connection attempt; on successive connection attempts, it chooses the next COP in sequence.

    For each COP, only the first known IP address is used. If both IPv6 and IPv4 addresses are known, only the first known IPv6 address is used.

    If a COP is known to be down, it is skipped unless the time period given by the COPDownRetry attribute has expired.

    Note: The COP definitions is retained for the life of OLE DB Provider for Teradata.

    NumberOfCOPs is zero

    Load balancing is disabled. OLE DB Provider for Teradata only attempts to connect to the specified server name.

    The specific COP names are not used, and all known IP addresses (both IPv6 and IPv4) for the name are used in attempting a connection.

    Note: This option is more limited than not specifying NumberOfCOPs; for that option OLE DB Provider for Teradata also tries to use the name of the first COP.

    A DNS caching problem might occur when utilizing load balancing with DNS Round Robin on clients running on Windows Server 2003. For more information on this problem in Windows 2003, please refer to Microsoft Knowledge Base Article 318803.