Sybase 12.4.2 manual Using multiple dbspaces, Transaction log file, Across multiple disks, 445

CHAPTER 12 Managing System Resources

Figure 12-3: Internal disk striping

The example above shows disk drive A has two 2GB partitions (a and b) and two 500MB (or .5GB) partitions (c and d). There are three other 1GB disk drives (E, F, and G). You should create your database on partition a, then add dbspaces for E, c, F, b, G and d.

Using multiple dbspaces

	Using multiple dbspaces allows your IQ and temporary data to be broken down
	into multiple operating system files or partitions. These files can then be spread
	across multiple disks.
	Like disk striping, randomness can be created by placing successive database
	files across multiple drives. You can create additional segments for your IQ and
	temporary data with the CREATE DBSPACE command.
When to create	When possible, allocate all dbspaces when you create a database.
dbspaces	If you add dbspaces later, IQ stripes new data across both old and new
	dbspaces. Striping may even out, or it may remain unbalanced, depending on
	the type of updates you have. The number of pages that are “turned over” due
	to versioning has a major impact on whether striping is rebalanced.

The transaction log file

The transaction log file contains information that allows Adaptive Server IQ to recover from a system failure. Adaptive Server IQ does not use the transaction log to restore an IQ database, to recover committed IQ transactions, or to restore the Catalog Store for an IQ database. All databases require a transaction log.

445