Comparison between local tablespace management and dictionary tablespace Management

The local tablespace management greatly improves the management efficiency and database performance compared with the dictionary tablespace management. Its advantages are as follows:

1. Reduced recursive space management

The local tablespace is managed and allocated by yourself, rather than the tablespace managed by the system like a dictionary, the local tablespace maintains a bitmap in each data file of the tablespace to track the remaining space and usage of the block in this file, and timely update (in principle, a bitmap area is added to the header of the data file in each tablespace to record the usage of each partition. Each table File Header has 64 kb for bit map. Every time a zone is used or released for reuse, Oracle updates this record in the data file header to reflect this change ). This update only modifies the table space quota and does not perform any update operations on other data dictionary tables. Therefore, no rollback information is generated, which greatly reduces space management and improves management efficiency. At the same time, the local tablespace can be managed in a uniform size allocation mode (Uniform), which greatly reduces space management and improves database performance.

2. the system automatically manages the extents size or uses the unified extents size.

The local tablespace can be automatically allocated (autoallocate) or uniformly distributed (Uniform). The system determines the size of extents automatically, the unified size allocation (Uniform) is the extents size specified by the user. Both methods improve the space management efficiency.

3. Reduced competition between data dictionaries

Because the local tablespace is managed by maintaining a bitmap of each data file to track and update the space of the blocks in the file, this update only modifies the quota of the tablespace, other data dictionary tables are not involved, which greatly reduces competition between data dictionary tables and improves database performance.

4. No rollback information is generated.

In addition to updating the table space quota, the local tablespace space management does not modify any other data dictionary tables. Therefore, no rollback information is generated, which greatly improves the running speed of the database.

5. No need to merge adjacent spaces

Because the extents space management of local tablespace management will automatically track the adjacent residual space and be automatically managed by the system, so there is no need to merge adjacent residual space. At the same time, all extents for local tablespace management can have the same size, which reduces space fragmentation.

6. Reduced Space fragments

7. Better management of temporary tablespace