12.3. Actions of operator-technologists

A special archive (magazine) recorded the following statement, executed on a workstation:

1. Input / output of the system (system logon / logout).

2. Acknowledgment alarm (alarm acknowledgment).

3. Changes of process variables (variable changes).

4. Changing the system if it is permitted (tuning).

This magazine is also stored in an SQL database and can be stored on the local computer (the operator's station), and centrally on the server (for example, at the same place where archives are stored alarm systems). Journal of the operator is displayed in tabular form and in appearance very similar to the alarm log. In it, as a minimum, showing:

1. The name of the operator.

2. Rights or access level of the operator.

3. Date and time of action.

4. Type of the act (eg, change setting).

5. Comment of the operator (if required).

In some systems, the log of actions of the operator and the alarm log is stored in a database and displayed in a single form. This is due to the fact that in both cases, the registration is event-based approach.

12.4. System architecture archiving

Let us consider how the archive can be deployed in a real system of government? Much, of course, depends on the system itself - a multi-vendor approaches to archives are somewhat different. Below we consider the most commonly used schemes:

1. Each operator station accumulates on your hard drive your own archive (or a certain part of the archive) irrespective of the other stations. This station has access both to the archive, and to the archives stored at the next station. Typically, each operator station is installed DBMS SQL (for example, a free version of Microsoft SQL Desktop Engine) for logging alarm and log of actions of the operator. In many systems, Archive of process variables are also recorded in the local database. It is worth considering that if such a scheme, archives, stored at different stations are not synchronized and therefore may differ significantly from each other. The above organization archiving more typical for systems with a single operator stations (Fig. 1 - 60).

Fig. 1 - 60. Archiving system for single operator stations

2. When a client-server architecture, carrier-grade (Fig. 1 - 61), history is collected and stored on a shared server. In the case of the redundant pair of servers, the system provides the identity stored on them copies of the archive, undertake a periodic synchronization. Operator stations are on-demand archive data is the total server (or servers) that is fully consistent with the overall client-server concept of building a top-level process control systems. Working with archives, as in the previous case, is organized with the help of database based on SQL.

Fig. 1 - 61. Archiving system for client-server architecture

3. For long term storage of history often emit a single central archive server (central archive server, CAS). Typically, a powerful server platform with high-capacity drives, or even a RAID-array. The main purpose of CAS - a collection and storage technology stories for several years. CAS takes the historical data from a common server, provides storage and delivers them to the operator stations (as, indeed, any others called them to the client). This scheme allows the backup server and a general release of operator stations of a resource problem as a collection of stories. Describes the architecture depicted in Fig. 1 - 62. In some systems, the CAS server is reserved. Many manufacturers of automated process control system called the central repository of archival data vogue "HISTORIAN", but the essence remains the same.

Fig. 1 - 62. Archiving system based on CAS server

To work with databases in the history of most modern systems use DBMS MS SQL Server, at least - Oracle.

What requirements must meet the archiving system?

1. Large depth (length) archive. This is reflected in the ability of continuous archiving of process parameters within a few years. But even after the file reaches its maximum size (for example, in the case of filling the hard drive), the system should not stop the backup. This is implemented as follows. Archive accumulates in the form of consistently produced parts (partitions, partitions) of a certain size. When the total size of all partitions reaches alarming proportions, the system automatically sends the oldest partition on the Backup-Server, or carries out their record on a removable storage device, thereby freeing up precious space under the new parts.

2. Performance (speed archiving) and the maximum number of parameters stored in the archive. This is achieved by modifying the standard database (eg, add-on SQL-server), which allows for higher speed operation of the database than in the usual office applications. For example, a product of Wonderware Industrial SQL Server version 9.0 allows you to record up to 2 000 analog variables in the second and supports of up to 60 000 parameters (of process variables). About the same speed archiving system has SIMATIC PCS7 Central Archive Server, but that, by the assurance of the manufacturer, supports up to 120 000 options.

3. Support for open communication protocols. Access to the archive from clients should be possible using standard, well-known protocols, eg, OPC, or using SQL-queries. This requirement stems from the fact that the archive is used not only the operator's station included directly in the CAM, but also to other users such as application servers MES, remote clients, workstation, shop superintendent, etc.