This section applies only if you (or the database administrator) are not using the automatic undo management feature or the PGA memory management feature, or both, of Oracle Database. Automatic memory management and PGA memory management are enabled by default, and their use is highly recommended. For explanations of these features, see:
The section about automatic undo management and undo segments in Oracle Database Concepts
The section about PGA memory management in Oracle Database Concepts
If you are not using automatic undo management and if the rollback segment is not large enough, an attempt to create a spatial index will fail. The rollback segment should be 100*n bytes, where n is the number of rows of data to be indexed. For example, if the table contains 1 million (1,000,000) rows, the rollback segment size should be 100,000,000 (100 million) bytes.
To ensure an adequate rollback segment, or if you have tried to create a spatial index and received an error that a rollback segment cannot be extended, review (or have a DBA review) the size and structure of the rollback segments. Create a public rollback segment of the appropriate size, and place that rollback segment online. In addition, ensure that any small inappropriate rollback segments are placed offline during large spatial index operations.
If you are not using the PGA memory management feature, the database parameter SORT_AREA_SIZE affects the amount of time required to create the index. The SORT_AREA_SIZE value is the maximum amount, in bytes, of memory to use for a sort operation. The optimal value depends on the database size, but a good guideline is to make it at least 1 million bytes when you create a spatial index. To change the SORT_AREA_SIZE value, use the ALTER SESSION statement. For example, to change the value to 20 million bytes:
ALTER SESSION SET SORT_AREA_SIZE = 20000000;