IDR CDC for Informix log_api_switch_log_num_pages parameter

Informix database manages the log switching in most situations. However, there are some cases such as refresh where it is beneficial for IDR to force a log switch on the Informix database. Refresh of a set of tables will cause IDR to stop reading logs, query the source (Informix) tables and load them into the target tables. Once the tables have finished loading, IDR will start reading logs (aka "mirroring") where it left off to replicate the changes made.

In order to reduce the time required to position (search for LSN) the Informix CDC API log reader after the refresh operation, the IDR product will prior to the refresh attempt to force an Informix database transaction log switch. The purpose of the log_api_switch_log_num_pages parameter (default value is 200, max 200000) is to ensure that mirroring starts quickly. IDR will check if the current log pages is greater than log_api_switch_log_num_pages, and if so, IDR will force Informix to perform a log switch. Setting log_api_switch_log_num_pages parameter to large values simply makes the Informix CDC API spend more time seeking/searching into the log to find the first log records matching the IDR "bookmark" position (containing the Informix log LSN). If you prefer IDR to not switch logs setting the parameter to maximum will mostly prevent IDR from forcing log switches.