The index can be either updated automatically or manually. Automatic updating is usually best if you have a fairly continuous stream of changes to the data. Manual updating is usually better when you do batch updates. Automatic updates are enabled by default, and controlled with the SYSMETAINDEX table. SYSMETAINDEX contains the name of the index, the period to wait between checks of the index, and the amount of new data that will trigger the update. By default it will wait an hour, and update if there are 1,000,000 bytes of new data.

These numbers should be adjusted to suit the data you have, and the rate at which it occurs. It may require some trial and error to get optimal settings for WAIT and THRESH, as you balance the extra load caused by indexing the data against the extra work performed when searching the changed records.