Extended memory is defined as memory greater than 4 GB RAM which is available for use by applications, hence usable to support memory-based libraries.
Conventional memory is defined as the memory that is below 4 GB in 32-bit environments and all of the memory in 64-bit environments.
Using the MEMLIB and MEMCACHE options, you can create memory-based SAS libraries. Depending on your operating environment, extended memory or conventional memory is used to support these memory-based libraries.
Using memory-based libraries reduces I/O to and from disk, improving SAS performance. Memory-based libraries can be used in several ways:
After operating system setup is complete for the SAS platform, MEMLIB and MEMCACHE system options and the MEMLIB option in the LIBNAME statement are available to access memory-based libraries.
In Windows operating environments, 32-bit processing uses 2 GB of physical memory for the operating environment, and the remaining 2 GB of physical memory is available for use by applications.
Some Windows operating environments do not support extended memory. In operating environments where extended memory is not supported or installed, SAS uses conventional memory to support the MEMLIB and MEMCACHE options.
Following are the OS requirements to use the MEMLIB and MEMCACHE options:
Note that Windows 64 OS 16 TB of virtual address space removing need for extended memory. SAS uses the available conventional memory to support the MEMLIB and MEMCACHE options.
It is possible to exhaust system memory and thus cause system failure. You can use the MEMMAXSZ option to limit the amount of system memory that SAS allocates for the MEMLIB and MEMCACHE options.
MEMMAXSZ System Option: Windows
Specifies the maximum amount of memory to allocate for using memory-based libraries in Windows operating environments
Valid in: | configuration file, SAS invocation |
Category: | System Administration: Memory |
PROC OPTIONS GROUP= | MEMORY |
Default: | 2G |
Windows specifics: | all |
MEMBLKSZ System Option: Windows
Specifies the memory block size for memory-based libraries for Windows operating environments.
Valid in: | configuration file, SAS invocation |
Category: | System Administration: Memory |
PROC OPTIONS GROUP= | MEMORY |
Default: | 16M |
Windows specifics: | all |
Part II: Processing SAS Libraries as Memory-Based Libraries
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