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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.
Factors that affect the query planWhen the optimizer determines the query plan, it assigns a cost to each possible plan and then chooses the plan with the lowest cost. The optimizer analyzes several factors to determine the cost of each query plan.
Effect of OPTCOMPIND on the query planThe OPTCOMPIND setting influences the access plan that the optimizer chooses for single and multiple-table queries. You can change the value of OPTCOMPIND within a session for different kinds of queries.
Multitable queryFor join plans, the OPTCOMPIND setting influences the access plan for a specific ordered pair of tables.

Multitable query

For join plans, the OPTCOMPIND setting influences the access plan for a specific ordered pair of tables.

Set OPTCOMPIND to 0 if you want the database server to select a join method exactly as it did in previous versions of the database server. This option ensures compatibility with previous versions.

If OPTCOMPIND is set to 0 or set to 1 and the current transaction isolation level is Repeatable Read, the optimizer gives preference to the nested-loop join.

Important: When OPTCOMPIND is set to 0, the optimizer does not choose a hash join.

If OPTCOMPIND is set to 2 or set to 1 and the transaction isolation level is not Repeatable Read, the optimizer chooses the least expensive query plan from among those previously listed and gives no preference to the nested-loop join.