Applications share resources at the database layer, including disks, the transaction log, and data cache.
One database may have 2^31 (2,147,483,648) logical pages. These logical pages are divided among the various devices, up to the limit available on each device. Therefore, the maximum possible size of a database depends on the number and size of available devices.
The "overhead" is space reserved to the server, not available forany user database. It is:
size of the master database,
plus size of the model database,
plus size of tempdb
(12.0 and beyond) plus size of sybsystemdb,
plus 8k bytes for the server's configuration area.
Issues at the database layer include:
Developing a backup and recovery scheme
Distributing data across devices
Auditing affects performance; audit only what you need
Scheduling maintenance activities that can slow performance and lock users out of tables
Options to address these issues include:
Using transaction log thresholds to automate log dumps and avoid running out of space
Using thresholds for space monitoring in data segments
Using partitions to speed loading of data
Placing objects on devices to avoid disk contention or to take advantage of I/O parallel.
Caching for high availability of critical tables and indexes