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AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Performance GuideThe HCL OneDB™ Performance Guide describes how to configure and operate your HCL OneDB™ database server to improve overall system throughput and to improve the performance of SQL queries.
Queries and the query optimizerThese topics describe query plans, explain how the database server manages query optimization, and discuss factors that you can use to influence the query plan. These topics also describe performance considerations for SPL routines, the UDR cache, and triggers.
The query planThe query optimizer evaluates the different ways in which a query might be performed and determines the best way to select the requested data. During this evaluation, the optimizer formulates a query plan to fetch the data rows that are required to process a query.
Sample query plan reportsThe topics in this section describe sample query plans that you might want to display when analyzing the performance of different kinds of queries.
Key-first scanThis topic shows a sample query that uses a key-first scan, which is an index scan that uses keys other than those listed as lower and upper index filters.

Key-first scan

This topic shows a sample query that uses a key-first scan, which is an index scan that uses keys other than those listed as lower and upper index filters.

Figure 1: Partial SET EXPLAIN output for a key-first scan

create index idx1 on tab1(c1, c2);

select * from tab1 where (c1 > 0) and ( (c2 = 1) or (c2 = 2))
Estimated Cost: 4
Estimated # of Rows Returned: 1

1) pubs.tab1: INDEX PATH

    (1) Index Keys: c1 c2 (Key-First) (Serial, fragments: ALL)
		 Lower Index Filter: pubs.tab1.c1 > 0
		 Index Key Filters:  (pubs.tab1.c2 = 1 OR pubs.tab1.c2 = 2)

Even though in this example the database server must eventually read the row data to return the query results, it attempts to reduce the number of possible rows by applying additional key filters first. The database server uses the index to apply the additional filter, c2 = 1 OR c2 = 2, before it reads the row data.