Applications share resources at the database layer, including disks, the transaction log, and data cache.
One database may have 231 (2,147,483,648) logical pages. These logical pages are divided among 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.
“Overhead” is space reserved to the server, and is not available for any user database. The overhead is calculated by summing the:
Size of the master database, plus
The size of the model database, plus
The size of tempdb, plus
(For Adaptive Server version 12.0 and later) the size of sybsystemdb, plus
8KB for the server’s configuration area.
At the database layer, issues that affect overhead include:
Developing a backup and recovery scheme
Distributing data across devices
Running auditing
Efficiently scheduling maintenance activities that can slow performance and lock users out of tables
Address these issues by:
Automating log dumps with transaction log thresholds to avoid space problems
Monitoring space with thresholds in data segments
Adding partitions to speed loading of data and query execution
Distributing objects across devices to avoid disk contention or to take advantage of I/O parallelism
Caching for high availability of critical tables and indexes
