Metadata, user data, and reserved area
As with blobspaces and dbspaces, when you create an sbspace, you assign to it one or more chunks. The first chunk of an sbspace always has three areas.
The following are the three areas of the first chunk of an sbspace:
- Metadata area
- Metadata identifies key aspects of the sbspace and each smart large object stored in the sbspace, and enables the database server to manipulate and recover smart large objects stored within.
- User-data area
- User data is the smart large object data stored in the sbspace by user applications. The chunk has up to two user-data areas.
- Reserved area
- The database server allocates space from the reserved area to either the metadata or user-data area when more space is required. The chunk has up to two reserved areas.
For information about correctly allocating metadata and user data for sbspaces, see Size sbspace metadata and the HCL OneDB™ Performance Guide.
When you add a chunk to an sbspace, you can specify whether it
contains a metadata area and user-data area or whether to reserve
the chunk exclusively for user data. You can add more chunks at any
time. If you are updating smart large objects, I/O to the user data
is much faster on raw disks than cooked chunk files. For instructions
on how to create an sbspace, add chunks to an sbspace, or drop a chunk
from an sbspace, see Manage disk space.
Important: Sbspace metadata is always logged, regardless of
the logging setting of the database.