Sybase 12.4.2 manual Other ways to get more memory, Options for Java-enabled databases, 438

Overview of memory use

•On Solaris systems with more than 4GB of memory, the file system buffer cache competes with IQ's buffer cache less, so you may decrease performance by turning off file system buffering.

•On NT systems, under certain loads and configurations, disabling the file system buffer cache can likely improve performance.

As of Version 12.4.2, file system buffering is turned off by default for newly created IQ databases.

To disable file system buffering for existing databases, issue the following statement:

SET OPTION "PUBLIC".OS_FILE_CACHE_BUFFERING = OFF

You can only set this option for the PUBLIC group. You must shut down the database and restart it for the change to take effect.

Note Solaris does not have a kernel parameter to constrain the size of its file system buffer cache. Over time, the file system buffer cache grows and displaces the IQ buffer cache pages, leading to excess operating system paging activity and reduced IQ performance.

NT can bias the paging algorithms to favor applications at the expense of the file system. This bias is recommended for IQ performance. See Chapter 5, “Performance and Tuning Tasks” in the Adaptive Server IQ Installation and Configuration Guide for Windows NT for details.

Other ways to get more memory

In certain environments, you may be able to adjust other options to make more memory available to Adaptive Server IQ.

Options for Java-enabled databases

The JAVA_HEAP_SIZE option of the SET OPTION command sets the maximum size (in bytes) of that part of the memory that is allocated to Java applications on a per connection basis. Per connection memory allocations typically consist of the user's working set of allocated Java variables and Java application stack space. While a Java application is executing on a connection, the per connection allocations come out of the fixed cache of the database server, so it is important that a run-away Java application is prevented from using up too much memory.

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