User Guide > Data Ship Performance Optimization > Data Ship Limitations
 
Data Ship Limitations
Some resource constraints limit the use of data ship optimization. Most limitations are related to data type mismatches. Data type mismatches are handled by a transformation of the data, but certain data types from different sources are incompatible for a selected target. Typically, these data type mismatches are most notable for numeric precision.
The following is a list of cases where use of the Data Ship optimization is not recommended.
Data Source Type
Limitation
Microsoft SQL Server
When using Microsoft SQL Server with the bcp utility, you might get data type mismatch errors if you are using BLOB or CLOB data types.
To Netezza
Netezza cannot be the data ship target for source tables containing data of type BINARY or VARBINARY (for example Oracle).
Netezza cannot be the data ship target for tables with LONGVARCHAR or VARCHAR columns more than 64 KB long, because creation of the temporary table fails.
When Netezza is the data ship source, data types of FLOAT or DOUBLE might lose precision because of rounding of values sent to a target of a different type.
Netezza to Sybase IQ
With data ship from Netezza to Sybase IQ, NULL values are replaced with zeroes, which results in different query results than when data ship is disabled.
Sybase IQ or Netezza to Oracle
When Sybase IQ or Netezza data sources use Oracle as a data ship target, trailing spaces sent in the shipped table are trimmed in the result sets with the Oracle table.
Sybase IQ to Netezza
When Sybase IQ data sources use Netezza as the data ship target can cause a data mismatch because the Netezza database appends a padding space character in result set data.
To Oracle
If an Oracle database is a data ship target and the transferred data contains UTF-8-encoded East Asian characters, a column length limitation exception can occur.
Oracle databases with a UTF-16 character set does not have this problem.
To Sybase IQ
If you are moving data of type FLOAT to a Sybase IQ database, the scale of the data can be lost because of the way that the Sybase IQ JDBC driver handles the FLOAT data type.
Sybase IQ Type4 Driver
Sybase IQ Type4 driver appears to lose the precision of time stamp columns by promoting or demoting it. To avoid this issue, use the Sybase IQ Type2 driver.
Teradata
Teradata controls the number of concurrent FastLoad and FastExport tasks using the MaxLoadTasks and MaxLoadAWT parameters. Excess FastLoad or FastExport tasks are rejected.
The maximum number of sessions for each FastLoad or FastExport job is limited to the number of AMPs of the Teradata database. Eight sessions work well for most scenarios.
Teradata’s implementation of UNION does not follow the SQL standard, which can result in a data mismatch when the data is shipped to Teradata.
A row fetch size bigger than 64 KB causes a Teradata error. Refer to Teradata documentation for the best solution to this problem.
Teradata FastLoad requires that the target table be empty. If the target Teradata table is not empty, JDBC is used to load data into the table.
To Vertica
For Vertica, the maximum length of a BINARY or VARBINARY column is 65000.