Managing memory of Analysis Services instance

Configuring the memory of your instance Analysis Services

Microsoft Analysis Services (SSAS) has a capacity to improve performance by making data in cache. SSAS can benefit from increased physical memory. You will find below a summary of the limits of memory 32Bit and 64Bit.

If your operating system and Analysis Service are in 32Bit
By default in a 32bit environment, the process "Analysis Service" is limited to 2 GB of memory.

The modification of the / 3GB memory pushes the limits by default. If you want to allocate more than 2Gb to "Analysis Service", you can add the / 3GB switch in the boot.ini to allow "Analysis Service" to use up to 3 GB of memory. Keep in mind that the / 3GB switch reduces the memory available by the Kernel to 1Gb and thus system contention problems can occur.

CautionIf the machine has more than the 16Gb / 3GB is not supported.
The 3GB switch will impact all the software on the server that can allocates more than 2Gb. Such as SQL Server Engine

Example :
- By default: 2Gb virtual memory for process SSAS and 2Gb for the Kernel.
- /3GB : 3Gb of virtual memory for process SSAS and 1GB for kernel

If your operating system is in 64Bit and Analysis Service in 32 Bit
If your system is operating in 64-bit and Analysis Service in 32 bits, so the process "Analysis Service" is limited to 4 GB of memory.

If your operating system and Analysis Service are in 64Bit
For 64-bit machine, you have no limitations, other than that you configured in the properties of the SSAS instance (and of course the available memory on the machine)

Configuring an instance SSAS
You can configure the properties for your SSAS instance from the configuration file MSMDSRV.INI. Before you make a configuration change, you should always make a backup of the file:% \ Microsoft SQL Server \ "Instance Name" \ OLAP \ Config \ msmdsrv.ini. All changes are taken into account immediately after you save the file and without restarting the instance.

By default an instance "Analysis Service" is set to assume almost all of the memory. The default values are appropriate for the majority of servers that have a single instance and OLAP (Analysis Services). From the moment or you  add an additional instance of OLAP or SQL Server in your server, you must change some settings.

As for SQL Server with the parameter MEMORY MAX( ), We recommend that you change the property values of the memory instance "Analysis Service" on your server multi-instances. All the properties below the value of which is less than 100 are in% while all values greater than or equal to 100 are in Bytes:

TotalMemoryLimit : 85
LowMemoryLimit : 75

Unlike SQL Server, the value TotalMemoryLimit is not an absolute limit because SSAS can  run a query or processing far exceed this value. Take this as an objective value that the engine is fixed.

Michel Degremont| Microsoft EMEA
Product Support Services Developer -SQL Server Core Engineer |

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