A database is always considered integral unless it presents problems. This may sound a little bit funny, but the general approach, in real life, is to run an application over a database until something wrong happens. To avoid surprises, certain procedures can be preventively taken to guarantee that the database is always available. These procedures…
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The files that make up a Zim application are implemented in your operating environment’s file system. This section discusses how the various types of files are mapped onto that file system. This section looks only at the default organization. The default organization can be changed using Zim tools. Database Directory By default, Zim stores all…
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An application is composed of a number of different types of files including directory files entity sets and relationship files application program files compiled application program files You can control where these files are located. Changing the location of files can be useful for increasing performance (locating files on the network nodes and servers where…
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Zim uses the operating environment’s file system to store data, programs, data dictionary definitions, configuration information, and work files. Use the ZIMFILES utility to obtain a complete list of database and document file names in your application. The following files are created by or for Zim. TYPE FILE NAME USE Database zimnnnn This file stores entity…
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Each Zim database has its own object dictionary. All objects (i.e. entity sets, forms, variables, and so on) that are described in the object dictionary are created in a Zim directory. Normally, an application developer creates the Zim directories that are used within one particular database. A foreign directory, on the other hand, is a…
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File management can be adapted to the resources available in the operating environment. To manage files efficiently, it is important to know how to control the number of files that the system has open at any one time how to estimate file space how to control the growth of a file how to pre-allocate space…
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Deadlocks A deadlock condition occurs when two users have to wait for each other in order to complete their respective transactions. For example, one user’s transaction needs records currently being used by a transaction started by another user. The second user’s transaction in turn requires records that the first user’s transaction is holding (while it…
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A well-designed database application is of no use if data and the application are not available 100% of the time. Data loss and corruption are not common in most systems, but occasional occurrences are unavoidable. Some of the events that can cause data loss include the following: Event Description User error Individual records, or even…
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The driver provides a login dialog under one of two conditions. The login appears if the application using the driver passes it a blank user id or password the user id or password variables are not defined in the registry The User ID and Password passed to the driver from the application override those defined…
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Even though per user entity sets are private and only seen by the user that created them, they can still be available to an ODBC Driver connection by means of the Dynamic Creation of a Data Source, which informs the work path that contains the per user entity sets. When the third party software connects…
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