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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Zim supports Microsoft Open Database Connectivity Drivers (ODBC, defined by Microsoft as a standard way for applications to access data stored in database files) which allows third-party tools to access a Zim database via the Zim ODBC Driver. This driver is used to access data from a Zim database that is either local to the…
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Note: In Zim, constant strings can be represented either surrounded in single quotes (‘) or double quotes (“). In SQL, constant strings are surrounded by single quotes (‘) whereas identifiers are surrounded by double quotes (“). statement ::= SELECT select | INSERT insert | DELETE delete | UPDATE update | passthroughSQL passthroughSQL ::= any statement…
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An ODBC Data Source to access a Zim database can be configured in two different ways: . Using the Zim ODBC Driver Setup to create a data source; . Using Zim language to dynamically create and maintain a data source tailored for specific needs like calling a third party software from within Zim. In both…
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If the server function requires parameters (called input host variables), these can be supplied by placing parameter markers in the syntax (indicated with a ‘?’) and then specifying the parameters as the second and subsequent arguments to $ServerFunction. Here is an example: change all orders where orderno = 1003 \ let RequiredByDate = $ServerFunc(‘trunc( ?,…
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The various XML technologies incorporated into ZimWeb may require references from one source to another (e.g. one XSLT stylesheet referencing another, or a reference to an external image in XSL-FO). The following explains precisely how references to other sources (URIs) are interpreted in different circumstances. URIs in XML generated by the Zim database agent…
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