Is the Oracle tablespace the difference between "local administration" and "Data dictionary" management? ____oracle

In the oracle8i version, Oracle has introduced a new way of tablespace management: a localized managed table space. Localized management means that Oracle no longer uses the data dictionary table to record the usage of the area inside the Oracle tablespace, but instead adds a bitmap area to the header of each table space's data file, where it records the usage of each area. Each time a zone is used, or released for reuse, Oracle updates the record in the header of the data file, reflecting the change. 　 The process of creating a localized managed table space: Syntax: CREATE tablespace table space name DataFile ' data file Details ' [EXTENT MANAGEMENT {Local {autoallocate | Uniform [SIZE inteter [k| M]]}} Keyword Extent MANAGEMENT local Specifies that this is a localized managed table space. For system tablespace, you can specify extent Mangement local only when you create the database because it is the first tablespace that was created when the database was built. In 8i, dictionary management is still the default way of managing, and when the local keyword is selected, it indicates that it is a locally managed table space. Of course, you can continue to choose a more detailed management style: is Autoallocate or uniform. In the case of Autoallocate, Oracle is used to determine the use of the block, and if uniform is selected, the size of each chunk can be specified in detail, and 1M size is used for each area if unspecified. Oracle has introduced this new approach to table space management, comparing the advantages of the following table space organization methods: 1. Localized management of tablespaces avoids recursive space management operations. This situation in the data dictionary management of the table space is frequent, when the use of the area in the table space changes, the data dictionary table information changed, and also used in the system table space in the rollback segment. 2. Localized management of the table space to avoid the corresponding table in the data dictionary to write free space, the use of space information, thereby reducing the competition in the Data dictionary table, improve the concurrency of space management 3. The localization management of the zone automatically tracks the free blocks in the table space, reducing the need for manual merging of free space. 4. The size of the area in the tablespace can be determined by the Oracle system, or by the database administrator specifying a uniform size, avoiding the fragmentation problem that has been a headache for the dictionary table space. 5. Manage the idle block from the data dictionary to manage the idle block by the header record of the data file, so as not to generate rollback information and no longer use the rollback segment in the system tablespace. Because it is managed by a data dictionary, it will record the relevant information in the data dictionary, resulting in rollback information. 　     Because of the above characteristics of this tablespace, it supports more concurrent operations within a table space and reduces reliance on data dictionaries.