| United States Worldwide |
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| United States Worldwide |
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Specifying the Store LocationIn order to support very large object spaces, a persistent store may span several files and/or raw disk partitions. To simplify adminstration this information is specified in a configuration file. The location of the configuration file, as an absolute pathname, is given to the OPJ Virtual Machine using the -store argument.For example: -store /usr/mjj/TestStore.pjc Configuration File FormatThe configuration file format is a sequence of ASCII characters, separated into sections that cover specific aspects of store management. These are Session, Log, Recovery and Store. A section is begun by its name in angle brackets and terminated by a new section name or the end of the file. Comments are specified by ## characters and continue until and end-of-line character is encountered.A persistent store has two parts, a log and the store proper. Ultimately all objects ends up in the store proper, and we will refer to this as the object store when we need to distinguish this from the log. The log is used during the stablization phase of a checkpoint, and during restart, to ensure that a stabilization appears atomic in the face of application or system failure. The location of the log and the object store must be provided in the configuration file. Both of these may be specified as an operating system file, or a raw (disk) partition. If performance is a serious consideration, it is advantageous to keep the log and the object store on separate disks, so that head movement is minimized. Simple applications with modest store sizes typically do not need to worry about this. Similarly raw partitions offer some performance benefits, but reduce flexibility and require more adminstration. Standard Filename ExtensionsYou may use any filename extensions that you choose, but we recommend that you consider observing the following convention:
Sample ConfigurationsMost applications will work correctly with a standard configuration and will only require the location of the log and store segments to be specified. As a convenience, three sample configurations are provided that correspond to small, medium and large application store sizes. The maximum store size for these three configurations is as follows:
To use these sample configurations, you must copy and edit them to localize the path to the log file and store segments. For instant prototyping, the configuration tmp.pjc, which places the log in /tmp/opj.pjl and the store in /tmp/opj.pjs can be used in single-user installations.
Last changed: Dec 7th 1999
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