The DB2 optimizer then queries system information and statistics stored in the DB2 system catalog to determine the best method of accomplishing the tasks necessary to satisfy the SQL request.
DB 2优化器然后查询存储在DB 2系统目录中的系统信息和统计信息，以确定完成满足SQL请求所必需的任务的最佳方法。
The two versions differ in internal details like the indexing system, optimizer, and storage engine.
这两个版本在内部细节上不同，如索引系统、优化器和存储引擎。
An entry is added to the system catalog to indicate to the query optimizer that such a remote index exists.
一个条目被添加到系统编目中，以向查询优化器表明存在那样的一个远程索引。
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