This book is addressed to specialists involved in the operation of large information systems built using the 1C: Enterprise technological platform, and is a set of methods and approaches to ensure the technological quality of information systems. When preparing the materials, the practical experience of the operation teams of large information systems on the projects of the Centers of Competence on Technological Issues of 1C (TSKTP) was used. The book contains theoretical information on the organization of operation and describes practical methods, provides an analysis of the settings of various components of the information system. In addition, basic methods for localizing and investigating problems are described, examples of solving specific application problems of operation are given.