Ensure enough converter threads and VPs

Loads and unloads other than raw and fast-format ones are likely to be CPU intensive due to conversion overhead. In such cases, conversion speed is likely to determine the load or unload speed. It is thus important to use sufficient conversion resources (that is, enough converter threads and VPs).

The number of converter threads that is required for a device depends on the relative speeds of the device and the CPU as well as the data types in the table being loaded or unloaded. CHAR and VARCHAR formats are the cheapest to convert. INT, DATE, SMFLOAT, and FLOAT are more expensive. DECIMAL and MONEY are among the most expensive formats to convert.

The plconfig file specifies the number of converter threads per device. You can override this value on the onpload command line with the -M option.

The number of converter VPs should be based on the conversion intensity of the load or unload and the number of physical CPUs on the computer. If the load or unload is expected to be highly intensive, you might want to specify the number of convert VPs to be the number of physical CPUs (or one fewer) to take advantage of all of the available CPUs. You can set the number of converter VPs in the onpload configuration file.

The database server and onpload client VPs might both be competing for the same physical CPU resources. To reduce contention, run only the number of VPs that are necessary on both the database server and onpload sides. However, if the number of database server VPs is already specified, you might have a choice only in the number of onpload VPs. In this case, the suggestions in the previous paragraph apply.

Too few converter threads and VPs can make conversion a bottleneck. However, too many converter threads can waste time in scheduling threads in and out of the VPs. In general, more than ten converter threads per VP is too many.

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