Each measure group in a cube is divided into
partitions, where a partition defines a portion of the fact data that is loaded
into a measure group. SQL Server Analysis Services (SSAS) on
SQL Server 2008 R2 Standard Edition allows only one partition per measure
group, while multiple partitions are allowed in the Enterprise
Edition.
Partitions are completely transparent to the end user,
but they have an important impact on performance and scalability. For example,
partitions can be processed separately and in parallel. They can have different
aggregation designs, although this was not implemented in
System Center 2012 – Service Manager.
You can reprocess a partition without affecting all the
other partitions in a measure group. Also, SSAS automatically scans only the
partitions that contain the necessary data for a query, which can vastly
improve query performance.
Cube partitioning is performed on every data warehouse
maintenance job run, which is hourly by default. The specific process module
that runs is named Manage Cube Partitions. It always runs after the Create Mart
Partitions step.
This dependency data is stored in the
infra.moduletriggercondition table.
The main dynamic link library (DLL), which
handles partitioning, is in the warehouse utility DLL,
Microsoft.EnterpriseManagement.Warehouse.Utility, in the PartitionUtil class.
Specifically, there is a ManagePartitions () method in the class that handles
all partition maintenance.
The data warehouse maintenance DLL,
Microsoft.EnterpriseManagement.Warehouse.Maintenance, and the data
warehouse online analytical processing (OLAP) DLL,
Microsoft.EnterpriseManagement.Warehouse.Olap, both call into Microsoft.EnterpriseManagement.Warehouse.Utility
to handle partitions during maintenance and cube deployment
This is why actual partition handling is in the common
warehouse utility DLL to avoid duplicating logic or code.
Cube Partitioning Maintenance performs the following
tasks:
- Create partitions
- Delete partitions
- Update partition boundaries
To do this, the Structured Query Language
(SQL) table etl.TablePartition is read to determine all the fact partitions
that have been created for a measure group. The following actions occur:
Start cube processing for each measure group in the
cube
Get all partitions from the Each measure group in
a cube is divided into partitions, where a partition defines a portion of the
fact data that is loaded into a measure group.
SQL Server Analysis Services (SSAS) on SQL Server 2008
R2 Standard Edition allows only one partition per measure group, while multiple
partitions are allowed in the Enterprise Edition.
Partitions are completely transparent to the end user,
but they have an important impact on performance and scalability.
For example, partitions can be processed separately and
in parallel. They can have different aggregation designs, although this was not
implemented in System Center 2012 – Service Manager.
You can reprocess a partition without affecting all the
other partitions in a measure group. Also, SSAS automatically scans only the
partitions that contain the necessary data for a query, which can vastly
improve query performance.
The main dynamic link library (DLL), which handles
partitioning, is in the warehouse utility DLL,
Microsoft.EnterpriseManagement.Warehouse.Utility, in the PartitionUtil class.
Specifically, there is a ManagePartitions () method in the class that handles
all partition maintenance.
The data warehouse maintenance DLL,
Microsoft.EnterpriseManagement.Warehouse.Maintenance, and the data warehouse
online analytical processing (OLAP) DLL,
Microsoft.EnterpriseManagement.Warehouse.Olap, both call into
Microsoft.EnterpriseManagement.Warehouse.Utility to handle partitions during
maintenance and cube deployment.
This is why actual partition handling is in the common
warehouse utility DLL to avoid duplicating logic or code.
Cube Partitioning Maintenance performs the following
tasks:
- Create partitions
- Delete partitions
- Update partition boundaries
To do this, the Structured Query Language (SQL) table
etl.TablePartition is read to determine all the fact partitions that have been
created for a measure group.
The following actions occur:
- Start cube processing for each measure group in the cube
- Get all partitions from the etl.TablePartition table for the measure group
- Delete any partitions that exist in the measure group but that are missing from the etl.TablePartition table
- Add any new partitions that have been created and that exist only in the etl.TablePartition table
- Update any partition that might have changed by matching each partition to the RangeStartDate and RangeEndDate in the etl.TablePartition table
Remember the following about cube processing:
Only measure groups that are targeted at facts contain
multiple partitions in SQL Server 2008 R2 Standard Edition. By default, all
measure groups and dimensions contain only one partition. Therefore, the
partition does not have any boundary conditions.
The partition boundaries are defined by a query binding
that is based on date keys that match up to the date keys for the corresponding
fact partition in the etl.TablePartition table.
Get all partitions from the etl.TablePartition table
for the measure group table for the measure group
Delete any partitions that exist in the measure group
but that are missing from the etl.TablePartition table
Add any new partitions that have been created and that
exist only in the etl.TablePartition table
Update any partition that might have changed by
matching each partition to the RangeStartDate and RangeEndDate in the
etl.TablePartition table
Remember the following about cube processing:
Only measure groups that are targeted at facts contain
multiple partitions in SQL Server 2008 R2 Standard Edition. By
default, all measure groups and dimensions contain only one partition.
Therefore, the partition does not have any boundary conditions.
The partition boundaries are defined by a query binding
that is based on date keys that match up to the date keys for the corresponding
fact partition in the etl.TablePartition table.
