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How To Fix SMMSS_ALERTS021 - This alert tracks the data cache hit ratio of SQL Server


SAP Error Message - Details

  • Message type: E = Error

  • Message class: SMMSS_ALERTS - Message class for MSSQL rz20 messages

  • Message number: 021

  • Message text: This alert tracks the data cache hit ratio of SQL Server

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  • Self-Explanatory Message

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    To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.

    Unfortunately, there isn't any extra information in this error notice.



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Smart SAP Assistant

  • What is the cause and solution for SAP error message SMMSS_ALERTS021 - This alert tracks the data cache hit ratio of SQL Server ?

    The SAP error message SMMSS_ALERTS021 indicates that there is an issue with the data cache hit ratio of SQL Server. This alert is part of the monitoring system in SAP that tracks the performance of the SQL Server database, specifically focusing on how effectively the database is utilizing its cache.

    Cause:

    The data cache hit ratio is a performance metric that indicates how often SQL Server is able to retrieve data from memory (cache) rather than having to read it from disk. A low cache hit ratio can indicate several potential issues:

    1. Insufficient Memory: The SQL Server instance may not have enough memory allocated to effectively cache data.
    2. High Workload: An increase in the number of queries or transactions may lead to more data being requested than can be cached.
    3. Poor Query Performance: Inefficient queries may lead to excessive disk reads.
    4. Fragmentation: High levels of fragmentation in the database can lead to inefficient data retrieval.
    5. Configuration Issues: SQL Server may not be optimally configured for the workload it is handling.

    Solution:

    To address the SMMSS_ALERTS021 error, consider the following steps:

    1. Monitor Memory Usage: Check the memory allocation for SQL Server. Ensure that it has enough memory to handle the workload. You can use SQL Server Management Studio (SSMS) to monitor memory usage.

    2. Optimize Queries: Review and optimize any poorly performing queries. Use SQL Server's execution plans to identify bottlenecks.

    3. Increase Memory Allocation: If the server has available resources, consider increasing the memory allocated to SQL Server.

    4. Database Maintenance: Perform regular maintenance tasks such as rebuilding indexes and updating statistics to reduce fragmentation and improve performance.

    5. Review Workload: Analyze the workload on the SQL Server. If there are spikes in usage, consider load balancing or scaling out the database.

    6. Configuration Review: Ensure that SQL Server is configured correctly for your environment. This includes settings related to memory, parallelism, and other performance-related configurations.

    7. Use Performance Monitoring Tools: Utilize SQL Server performance monitoring tools to gain insights into cache usage and identify areas for improvement.

    Related Information:

    • SQL Server Documentation: Refer to the official Microsoft SQL Server documentation for detailed information on performance tuning and memory management.
    • SAP Notes: Check SAP Notes related to SQL Server performance issues for any specific recommendations or patches.
    • Performance Counters: Use SQL Server performance counters (like Buffer Cache Hit Ratio) to monitor and analyze performance over time.

    By following these steps, you should be able to improve the data cache hit ratio and resolve the SMMSS_ALERTS021 alert in your SAP environment.

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