Underestimating space requirements for databases, users, and profiles leads to performance problems. This is because the database requires free disk cylinders to enable the growth of permanent, temporary, and spool space and to enable the growth of permanent journal tables.
These tables cannot share cylinders when you make your permanent, temporary, and spool disk space assignments. For databases with uneven or skewed data distribution, current space assignments may be much higher than normal to accommodate the skewed use. In such cases, global space accounting can help and space assignments can be normal (for example, an average value) because space is managed at a global level. For more information about global space accounting, see Global Space Accounting.
The best practice for the initial sizing of the disk space required by a database, user, or profile is to make a good estimate of the space these need when a database, user, or profile is created, and then to modify those assignments at a later time using MODIFY DATABASE, MODIFY USER, or MODIFY PROFILE requests as appropriate.
Consider the following disk space requirements when making disk space assignments for databases, users, and profiles.
| Disk Space Type | Purpose |
|---|---|
| Spool | Materializing volatile tables. |
| Temporary | Materializing global temporary tables. To materialize global temporary tables, temporary space must have enough empty disk cylinders to contain their rows. |