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# OPTIMIZE_FOR_SEQUENTIAL_KEY
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In SQL Server 2019, a new index option was added called OPTIMIZE_FOR_SEQUENTIAL_KEY that is intended to address an issue known as [last page insert contention](https://support.microsoft.com/kb/4460004). Most of the solutions to this problem that have been suggested in the past involve making changes to either the application or the structure of the contentious index, which can be costly and sometimes involve performance trade-offs. Rather than making major structural changes, OPTIMIZE_FOR_SEQUENTIAL_KEY addresses some of the SQL Server scheduling issues that can lead to severely reduced throughput when last page insert contention occurs. Using the OPTMIZE_FOR_SEQUENTIAL_KEY index option can help maintain consistent throughput in high-concurrency environments when the following conditions are true:
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In SQL Server 2019, a new index option was added called [OPTIMIZE_FOR_SEQUENTIAL_KEY](https://docs.microsoft.com/sql/t-sql/statements/create-index-transact-sql#sequential-keys) that is intended to address an issue known as [last page insert contention](https://support.microsoft.com/kb/4460004). Most of the solutions to this problem that have been suggested in the past involve making changes to either the application or the structure of the contentious index, which can be costly and sometimes involve performance trade-offs. Rather than making major structural changes, OPTIMIZE_FOR_SEQUENTIAL_KEY addresses some of the SQL Server scheduling issues that can lead to severely reduced throughput when last page insert contention occurs. Using the OPTMIZE_FOR_SEQUENTIAL_KEY index option can help maintain consistent throughput in high-concurrency environments when the following conditions are true:
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- The index has a sequential key
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- The number of concurrent insert threads to the index far exceeds the number of schedulers (in other words logical cores)
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For more information, see these articles:
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[CREATE INDEX - Sequential Keys](https://docs.microsoft.com/sql/t-sql/statements/create-index-transact-sql#sequential-keys)
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[CREATE INDEX - Sequential Keys](https://docs.microsoft.com/sql/t-sql/statements/create-index-transact-sql#sequential-keys)
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[Behind the Scenes on OPTIMIZE_FOR_SEQUENTIAL_KEY](https://techcommunity.microsoft.com/t5/SQL-Server/Behind-the-Scenes-on-OPTIMIZE-FOR-SEQUENTIAL-KEY/ba-p/806888)
When prompted, provide your input for Azure subscription ID, Azure resource group to create the resources in, and Docker credentials. Optionally, you can also provide your input for below configurations or use the defaults provided:
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- azure_region
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- vm_size - we recommend to use a VM size to accommodate your workload. For an optimal experience while you are validating basic scenarios, we recommend at least 8 vCPUs and 32GB memory across all agent nodes in the cluster. The script uses **Standard_L8s** as default.
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- vm_size - we recommend to use a VM size to accommodate your workload. For an optimal experience while you are validating basic scenarios, we recommend at least 8 vCPUs and 64GB memory across all agent nodes in the cluster. The script uses **Standard_L8s** as default. A default size configuration also uses about 24 disks for persistent volume claims across all components.
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- aks_node_count - this is the number of the worker nodes for the AKS cluster, excluding master node. The script is using a default of 1 agent node. This is the minimum required for this VM size to have enough resources and disks to provision all the necessary persistent volumes.
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- cluster_name - this value is used for both AKS cluster and SQL big data cluster created on top of AKS. Note that the name of the SQL big data cluster is going to be a Kubernetes namespace
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- password - same value is going to be used for all accounts that require user password input: SQL Server master instance SA account, controller user and Knox user
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