MTDATA – Phase Diagram Software from the National Physical Laboratory

 

 

 

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CREATE

Function:

This command allows the user to create a new (empty) database and to specify its size in terms of the approximate number of datasets to be stored. The new database may be given a title and/or protected by a password. In addition its name may be added to the MTDATA database configuration file. It will then appear on the list of active databases in subsequent MTDATA sessions as well as on the list held in memory during the current session.

Parameters:

database

password

title

estimated_datasets

update
Defaults:

password = <""> (A blank password gives no database protection)

title = <""> (No default title is given to a database)

estimated_datasets = 0

update = no
Examples:

create database="mydata" !

cre dat="slag" update=yes title="Data for slags - 12/3/93" !

cre data="projectx" password="XYZ123" !

cr da="minidata" title="A small database" estimate 10 !

creat data="maxidata" title="A big database" est 1000 !

Parameter values:

DATABASE takes the value <"database name">

Following the DATABASE parameter the user is expected to provide, in quotes, the name of the database to be created. No database of this name should already exist.

PASSWORD takes the value <"database password">

The PASSWORD parameter allows a password to be assigned to any new database. The chosen password should be specified in quotes. The contents of a password protected database cannot be listed out using the LIST_DATA command unless the correct password is given. If the PASSWORD parameter is not used in creating a new database, or a blank password is chosen, the database will NOT be password protected.

TITLE takes the value <"database title">

The TITLE parameter allows the user to assign a title to any new database. The desired title should be specified in quotes. The titles of all databases active during any MTDATA session can be inspected by invoking the STATISTICS command (see STATISTICS). Database titles should NOT contain the character "|" (a vertical line) as this may result in the database being inaccessible unless specifically authorised in the MTDATA permit file.

ESTIMATED_DATASETS takes the value <number>

The ESTIMATED_DATASETS parameter allows the user to specify the size of a new database to be created in terms of the approximate number of data items to be stored. If too small a number is given then the database file will be increased in size as necessary during the data loading process. If too large a number is given then some space will remain unused within the database file. The process of data loading and storage is most efficient if a reasonably accurate estimate is given for the number of datasets to be stored. By default zero is taken. 

UPDATE takes the values YES/NO

The UPDATE parameter is used to add the name of a new database to the MTDATA database configuration file (mtconfig.txt). This file contains an integer n followed by a list of databases, the first n of which are made available for use (or made "active") at the start of every MTDATA session. Any newly created database is added automatically to the in memory list of active databases (see STATISTICS command) but will only be available for use in subsequent MTDATA sessions if the database configuration file is UPDATEd. New databases are added at the (n+1)th position in the configuration file. All existing databases beyond this point therefore move down one place in the list.

YES is used to update the MTDATA database configuration file with the name of a new database about to be created. For the UPDATE to be successful the user must have permission to write to the mtconfig.txt file and this file must exist in the directory from which MTDATA is being run (the current directory).

NO is used to request that the MTDATA database configuration file is not updated.

General comments:

When the CREATE_DATABASE command is executed, the new (empty) database that is set up takes the form of two separate files. These files are given the extensions .dbs and .inx. They correspond to the database file itself and the database index file respectively. Deleting either file will destroy the database. It is important that .inx and .dbs files are NOT copied between different computer operating systems. 

There are four main types of error which may be encountered in creating a new database:

(a) A database (specifically an .inx file) with the same name already exists. This database may or may not appear on the list of databases currently active. An error message is issued as follows:

    FILE ALREADY EXISTS   PLEASE GIVE A NEW NAME

The simple remedy is to choose a different name for the new database. Alternatively the old (existing) database could be deleted if no longer required or renamed by modifying the names of the appropriate .inx and .dbs files along with their matching entry in the database configuration file (mtconfig.txt).

(b) The maximum number of active databases is reached. An error message is issued as follows:

    DATABASE CLOSED   TOO MANY ON CURRENT LIST

A new database (.inx and .dbs files) is created but does not appear on the list of databases currently active. The user should terminate the current MTDATA session, edit the database configuration file (mtconfig.txt) to replace the name of an old database with that of the new one (or add the new name at the top of the file) and then reload MTDATA.

(c) No mtconfig.txt file was found when MTDATA was loaded. An error message is issued as follows if UPDATE=YES is used:

    FILE CONTAINING DATABASE LIST NOT FOUND

    A new database (.inx and .dbs files) is created and appears on the active list. There is no mtconfig.txt file to update.

(d) The mtconfig.txt file is write protected.  An error message is issued as follows if UPDATE=YES is used:

    ERROR IN OPENING FILE CONTAINING DATABASE LIST

    A new database (.inx and .dbs files) is created and appears on the active list. The database configuration file (mtconfig.txt) is not changed.
 

 

Updated 22 June 2010