In Oracle, two important database parameters can be overridden at the session level to provide better overall performance:

HASH_AREA_SIZE
Specifies the maximum amount of memory, in bytes, to be used for hash joins.
Defaults as 2 * SORT_AREA_SIZE

SORT_AREA_SIZE
Specifies the maximum amount of memory, in bytes, to be used for query sorts.
Defaults as 65K

LogMiner must perform various metadata lookups on the data dictionary, particularly when utilizing online_catalog or hybrid strategies. These lookup queries involve a set of joins between several base tables that can benefit significantly from setting a higher hash area size than the default, especially in databases with a large number of database objects or where you have high redo generation rates.

In addition, although LogMiner reads the redo entries from disk in sequential order, it still performs a certain amount of sorting on the dataset before returning the result set to the client. By increasing the sort area size, this helps LogMiner in two distinct ways:

• Larger batch configurations can make use of more memory, which avoids spilling larger portions of the sort operation to disk.
• High-clustered windows of changes using the same SCN can be sorted more efficiently using memory rather than spilling to disk.