Procedure used to create the CE (global support) EPICS directory

Detailed Procedure to Manage Historical Trend Data

21JUL98

P. Sichta

Table of Contents

1.0 Introduction

2.0 References

3.0 Aliases, Environmental Variables, and Permissions

Starting the Channel Archiver
Channel Archiver Configuration Files
Viewing Channel Archiver Data

7.0 Archiving Channel Archiver Data

8.0 Historical Trend Data Collection Guidelines

Figure 1 – Sample Channel Archiver Conf. File

Figure 2 – Sample Historical Trend Directory

1.0 Introduction

This procedure provides a detailed description of how to use the Channel Archiver (CAR) to create and manage EPICS historical trend data filesat NSTX. CAR is one of several tools used in the EPICS community for acquiring historical trend data. Historical trend files contain a timestamp and the value of a process variable (PV), continuously sampled at slow, periodic interval. The historical data is viewed using a separate tool (XARR). Reference 4 describes Current Trend displays, which show a "live" update of a PV.

2.0 References

NSTX-WBS6-AD, Application Development Environment for CI&C.
NSTX-WBS6-CA, General Procedure to Create Applications for EPICS.
Channel/Frequency Archiver User’s Guide, Phillip Stanley, LANL www site.
NSTX-WBS6-AD-CT, EPICS Current Trend Data Management at NSTX.

3.0 Aliases, Environmental Variables, Paths, and PermiCARions

Aliases used : none

Environmental Variables : None

Paths : /epics/system/epics/epicsExtensions/extensions/bin/solaris

Permissions : Baseline CAR configuration files will be created by EPICS application developers, who must be in the Unix group ‘staff’.

4.0 Starting the Channel Archiver

The Channel Archiver can be started from any directory. A configuration filename and a directory filename must be specified on the command line :

/nstx : chan_arch /abspath/configfile.hst /abspath/directoryfile.dir

The historical trend file will begin filling immediately. The Channel Archiver will append to an existing data file, or create a new one if necessary. One or more data files are created daily, with a name similar to filename_x.htc:MM-DD-YY-000000. They reside in the same directory as the configuration file.

A window will appear on the launching terminal for each CAR session. This window may be minimized but not quit/exited. If the window is closed the data collection will stop.

Figure 3 shows the typical relationships between the config, directory, and data files.

The trending will normally be automatically started and stopped.

5.0 Channel Archiver Configuration Files

A CAR configuration file specifies all items for the historical trend. Specifically, a common sampling period (in seconds) and a list of each PV field. If no record field (extension) is specified, the record’s ".VAL" filed is assumed. Figure 1 shows a sample configuration file.

Figure 2 shows a historical trend directory containing several configuration files and data files.

A text editor is used to create or modify a configuration file.

CAR configuration files will be kept in the directory structure dedicated to each digraph, or application identifier. For example, if the digraph for a system is xx, then the configuration files for that system will be kept in /nstx/epicapps/xxApp/op/hist_trend .

The configuration files should end in .hst .

The directory files should end in .dir .

6.0 Viewing Channel Archiver Data

At present, a good method for viewing the historical trend data is lacking. XARR, an x-window based archived data viewer is very close to being available.

At present, the chan_retriever utility (reference 3) will list the trend timestamp & data to the screen (ASCII)

7.0 Archiving Data

The data storage file format is a complex arrangement which involve two file types, the daily data files (MM-DD-YY-000000) and the directory file (.dir). These two file types must be archived together. Furthermore, to limit the size of the directory file, it will be periodically skimmed (and recreated). To be able to view recent data after the directory file has been skimmed, a separate directory will be used to temporarily hold the "former" directory file and data files.

8.0 Historical Trend Data Collection Guidelines

Although the Channel Archiver is a sophisticated and high-performance tool, its initial use at NSTX will be limited to a simple configuration. This will simplify data management and enhance reliability.

There should be only one configuration file and one directory file per digraph. All devices needed for that digraph or trend group must be in the configuration file.

Use a trending PV sample rate of 60 seconds.

Figure 1 – Sample Configuration File for Historical Trend Acquisition

# file trlist.hst

# Channel Archiver Configuration File

# This file will archive the time remaining until first plasma.

# Rev 0. 16 JUL 98 By P. Sichta

!write_freq 300

!save_default 30

!file_size 24

ck_RemainSecAO

ck_RemainMinAO

ck_RemainHourAO

ck_RemainDayAO

A data cache will be filled with the value of the PVs every 30 seconds, and flushed to disk every 300 seconds. A new file will be created every 24 hours (midnight).

Figure 2 – Sample Directory for Historical Trend Files

/nstx/epicapps/ckApp/op/hist_trend :ls -lt

-rw-r--r-- 1 psichta staff 174 Jul 21 17:10 tr.dir.log

-rw-r--r-- 1 psichta staff 52320 Jul 21 17:07 07-21-98-000000

-rw-r--r-- 1 psichta staff 2152320 Jul 21 00:00 07-20-98-000000

-rw-r--r-- 1 psichta staff 2592 Jul 21 16:52 tr.dir

-rw-r--r-- 1 psichta staff 21 Jul 21 16:11 archiver_active

-rw-r--r-- 1 psichta staff 201 Jul 20 11:27 trlist.hst

List2.hst

List3.hst