II_DATABASE (Database Files) Location Guidelines
The instance default data location contains the master database (iidbdb), which stores information about all databases, their locations, and the users that can access them. By default, this location also contains all user databases, unless the database administrator specifies an alternate location for a database when creating it.
When choosing the data location, consider the following:
• Place database files on a separate disk from checkpoint, journal, and dump files to maximize chances for data recovery.
• Place database files on a separate disk from the work locations. Doing so prevents work operations that might fill the file system from having an impact on the data location, reduces fragmentation of both locations, and ensures sufficient reading bandwidth for the data location.
• On systems with three or more disks, do not place the database files on the same disk as your operating system. Administrators typically will want to improve reliability by avoiding a large amount of file create, open, and close activity on the operating system disk and not risk the operating system disk running out of space.
• Keep the usage of data file systems below 75 percent. Above this level, fragmentation will be more rapid and will degrade the efficiency of scanning operations. You will also need sufficient space to reorganize tables as part of database maintenance.
If you lose this location, Ingres will fail. You must replace the failed component, recreate the directory structure, and recover from checkpoint and journals all Ingres databases that use this location.
If you fill this file system, Ingres will fail. Free some space or allocate additional space, and restart Ingres if necessary.
The I/O bandwidth requirement for this file system depends on your reading and writing rates to the user databases using it (iidbdb requires almost none). Unless these are well-tuned OLTP databases, partial and complete scans of tables will dominate the reading. A larger Ingres cache will reduce reading, but will have almost no effect on substantial table scanning.