Secondary Database
First it must be stated that table design is a more logical work while index design is rather technical. In table design it might make sense to place certain fields (client, company code, ...) in the beginning. In index design, this is not advisable. Very important for an index is that it contains very selective fields in the beginning. Those are fields like object numbers. Not selective are client, company code, ...
Indexes should be small (few fields). The Database optimizer can combine two or more indexes to execute a query.
Indexes of one table should be disjoint (have few common fields), in order not to confuse the optimizer which index to use.
Note that each index slows the inserts into the table down. Updates are only slowed down if indexed fields are updated. In general, heavy inserted tables should have only few indexes while heavy selected tables might have more.
Logical Database
Using logical databases is a good method to write reports. Logical databases can be optimized centrally. But ensure that the structure of the logical database fits well to your report. Otherwise the effect can be the opposite.
Please clarify my doubts:
1. What is meant by secondary index?
2. What is the purpose of cursor?
No comments:
Post a Comment