The SYS_LOGPOS table contains information about the log intervals that the Logreader needs for Catchup.

Each row represents a log interval which is recorded with the approximate granularity defined with the parameter LogReader.SaveLogposInterval. A new row is added when the size of the current interval is reaching the value of SaveLogposInterval. The sum of the log interval sizes is approximately equal to the value of the parameter LogReader.MaxLogSize. A log interval row is deleted automatically when the distance of the represented log position from the latest recorded log interval head is bigger than LogReader.MaxLogSize.

The SYS_LOGPOS table is only used internally by Logreader while executing SYS_LOG table queries; the table does not contain any information to be used when designing applications that use Logreader.

If a query requests log records that are beyond the log intervals represented in SYS_LOGPOS, the query returns the error "Log overflow".