Micromod Micro-PWC: 53PW6000 MicroPWC Configuration Guide - Manual (Page 289)

Micro-PWC CONFIGURATION GUIDE
Utilities 269
At the top of the window is a list box which contains entries describing database usage on each node in the
local console group. Each entry includes:
• the node name
• the size of the disk space allocated for the database in KB
• the number of KB of the allocated space actually used (and the percentage)
• the total number of KB available on thenode’s hard drives
Note that as the Historical Database expands, additional disk space will be allocated for the database.
However, once allocated, space is never removed from the Historical Database’s allocation.
Data which is collected and stored in databases on the Micro-PWC is keyed (internally) for identification
within a database by either a time or a string. This key is assigned automatically by the Micro-PWC soft-
ware application which is performing the collection operation; it cannot be specified by the user. For exam-
ple, Historical Data and Archival Data are keyed by time, while Historical Block data and Archival Block
data are keyed by strings. Other applications can use both types of key to store data.
While the distinction between time keyed data and string keyed data is generally invisible to the user, the
Historical Database Maintenance window uses this feature. Information is displayed in the tagname list box
in the lower part of the window based on the type of key which is selected.
Use the radio buttons located above the tagname list box to select the key type to be used. When Time
Section (the default) is selected, all the tags which are keyed by time will be listed; select String Section to
list all the tags (if any) which are keyed by strings.
The data contained in the list box at the top of the Historical Database Maintenance window provides an
overview of the system usage by the Historical Database on each node. The tagname list box in the lower
part of the window provides information on system usage by individual tags. Data displayed here includes:
• the tagname (preceded by an S)
• the node or nodes where the point is part of the Historical Database
• the percentage of the node’s Historical Database used to store that point
This information can be used to fine-tune the data collection process to make the most efficient use of
resources. For example, you can view which collection items are using the most disk space, on which sys-
tems those collections are being stored, and where potential configuration changes could be made to bal-
ance the storage of data.
Following the list of standard time-based tagnames (preceded by S) the list contains an entry
b.eventhistory. This represents the Event Historian information which is also stored in the Historical Data-
base on the hard disk of each Micro-PWC on the system.
Following the b.eventhistory entry the window contains another alphabetical list of the tagnames in the
Historical Database on the system. These tagnames are preceded by the tilde character (~). The percent-
age displayed for a ~tagname represents the space used to store special information used by the system
software to synchronize the Historical Database when the system comes back up after a shutdown.
The Event Historian information is stored in a circular file; the size of the file is pre-set by the system soft-
ware. Therefore, no user actions can reduce the space allocated for the Event Historian information. How-
ever, the information about disk usage for each Historical Database Point can be used by configurers when
considering whether they can afford to store points at various collection rates.
✎ Note
The tagname list box lists historical database points in every
historical database on the Micro-PWC network (not just the local
node).