Oracle Apps DBA: Keeping E-Business Suite Alive · Module 3 · The database itself
Instance and database: two different things
Lesson 23 of 184 · 2 min
Memory and processes against FILES ON DISK. Getting this distinction wrong makes EVERY RECOVERY CONVERSATION CONFUSING. THE INSTANCE IS MEMORY AND PROCESSES. A shared memory area and a set of background processes, created when you start the database and destroyed when you stop it. It holds nothing permanently and it can be thrown away and rebuilt in seconds. THE DATABASE IS FILES ON DISK. Datafiles, control files, redo logs. That is where the data is, it survives everything, and it is the only thing that cannot be recreated. SO "THE DATABASE IS DOWN" IS AMBIGUOUS AND THE TWO MEANINGS NEED OPPOSITE RESPONSES. An instance that is not running is an availability problem: start it, and nothing is lost. A database whose files are damaged is a recovery problem, which is Module 5 and a different order of magnitude. The same sentence describes a five-minute fix and a four-hour restore. AND…
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In this module: Module 3 · The database itself
- 1Instance and database: two different things
- 2Starting and stopping, properly
- 3Tablespaces and datafiles
- 4Redo: the reason recovery is possible
- 5Archive log mode, and the day it was off
- 6Undo, and read consistency
- 7Parameters, and the ones that matter here
- 8The data dictionary, as a diagnostic tool
- 9Reading an error you have never seenFree preview
- 10What breaks: four database-tier failures
- 11Lab briefing · Stop it, start it, break it