Oracle Database 11 g - Online Public Access Catalog

CHAPTER 1 ■ INSTALLING, UPGRADING, AND MANAGING CHANGE 9global area (SGA) and the program global area (PGA)—will be automatically expanded andshrunk, based on the needs of the instance. All you need to do is set the values for two memoryrelatedparameters, memory_target and memory_max_target:• The memory_target parameter sets the system-wide usable memory and lets Oracle tuneboth the SGA and PGA, changing the values of the SGA and the PGA automatically basedon the demands of the running Oracle instance. You can dynamically change the valuefor this parameter using the alter system command.• The memory_max_target parameter sets the maximum value of memory Oracle can use.That is, the value you set for the memory_max_target parameter is the maximum value upto which you can adjust the memory_target parameter’s value.You can enable automatic memory management by setting the value of the memory_targetparameter and the memory_max_target parameter in the initialization parameter file whencreating a new database. You can also add them later to the initialization parameter file afterdatabase creation, but you have to bounce the database for automatic memory managementto take effect. Here’s an example showing how to specify the new memory-related parameters,if you started your database with an initialization parameter file:• memory_max_target = 500MB• memory_target = 350MB• sga_target = 0• pga_aggregate_target = 0This set of initialization parameters ensures that the server allocates 350MB of memoryto Oracle right away. Oracle will allocate this memory among the SGA and the PGA. You candynamically change the value of the memory_target parameter up to the maximum of 500MBset by the memory_max_target parameter. Note that you must set both the sga_target andpga_aggregate_target initialization parameters to 0 if you don’t want to set any minimumvalues for the sizes of the SGA and the PGA. For testing purposes on both Linux and Windowsservers, you can use as little as 120MB as the value for the memory_target parameter.We discuss the automatic memory management feature in detail in Chapter 3.PL/SQL Native Compilation ParameterIn Oracle Database 11g, it’s easier than ever to enable PL/SQL native compilation, which offersgreater performance benefits. In Oracle Database 10g, you had to use the initialization parameterplsql_native_library_dir to set a directory, as well as specify the plsql_native_library_sbdir_count parameter to enable native compilation of PL/SQL code. In addition, you also hadto use the spnc_commands file in the plsql directory under the Oracle home. In Oracle Database11g you use just one initialization parameter, plsql_code_type, to turn on native compilation.You don’t need a C compiler, and you don’t have to manage any file system DLLs either. Youdon’t need to create any directories or use the spnc_commands file. You can also adopt nativecompilation for Java. We explain native compilation in more detail in Chapter 4.