- Berkeley DB Reference Guide:
- Building Berkeley DB for VxWorks systems
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Berkeley DB currently disallows the DB_TRUNC flag to DB->open. The operations that this flag represents are not fully supported under VxWorks.
The DB->sync function is implemented using an ioctl call into the file system driver with the FIOSYNC command. Most, but not all file system drivers support this call. Berkeley DB requires the use of a file system supporting FIOSYNC.
The demo program should be built in a manner very similar to building Berkeley DB. If you want different or additional BSP build specifications you should add them by following the directions indicated in Building with Tornado 2.0 or Building with Tornado 3.1.
The demo program can be downloaded and run by calling the entry function dbdemo with the pathname of a database to use. The demo program will ask for some input keys. It creates a database and adds those keys into the database, using the reverse of the key as the data value. When complete you can either enter EOF (control-D) or quit and the demo program will display all of the key/data items in the database.
The Berkeley DB utility programs can be downloaded and run by calling the function equivalent to the utility's name. The utility functions take a string containing all the supported arguments. The program will then decompose that string into a traditional argc/argv used internally. For example, to execute db_stat on a database within an environment you would execute the following from the windsh prompt. Obviously you would change the pathname and database name to reflect your system.
-> db_stat "-h /tmp/myenvhome -d mydatabase.db"
The memory on VxWorks is always resident and fully shared among all tasks running on the target. For this reason, the DB_SYSTEM_MEM flag is implied for any application that does not specify the DB_PRIVATE flag. Additionally, applications must use a segment ID to ensure that different applications do not overwrite each other's database environments. See the DB_ENV->set_shm_key function for more information. Also, the DB_LOCKDOWN flag has no effect.
All tasks wishing to access a particular environment must run in the same application domain. The memory regions used by the environment are only accessible to the application domain. If more than one application domain attempts to access an environment simultaneously, the results are undefined but will likely lead to corruption.
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