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Sql activity monitor12/9/2023 ![]() ![]() The producer threads cannot store the packets into a buffer as the buffer is full. This means that some Producer threads are working slowly due to waiting for a resource such as CPU, memory grants, I/O, etc., or some Producer threads are simply blocked The Consumer cannot read the packets because the buffer (queue) is empty – meaning that the Producer threads do not supply or supply slow data into the buffer. During this process, three different scenarios that can cause excessive CXPACKET waits can be encountered: That data will then be read from the buffer by the consumer threads. One or more producer threads will produce packets and send them to a buffer. The query operator in charge of implementing this queue is called the Exchange operator. Communication between the producer and consumer thread is performed via the producer-consumer queue, which is actually a buffer. Each thread can be processed by a separate physical or logical CPU. The below diagram will be used for a better understanding of the SQL Server CXPACKET wait type and will help in its interpretation.įrom this diagram, we can see that whenever a parallel query execution can provide benefit to SQL Server, it will create multiple threads for that statement allowing for each parallel process to produce its own subset of data. This means that the query will be as fast as the slowest thread. When the parallel plan is used, the query is executed in multiple threads and the query can continue only when all parallel threads are completed. Generally speaking, the CXPACKET wait type is normal for SQL Server and it is an indicator that SQL Server is using a parallel plan in executing a query, which is generally faster comparing to a query executed in a serialized process. This wait type is directly related to parallelism and it occurs in SQL Server whenever SQL Server executes a query using the parallel plan. One thread is the “producer thread” and another thread is the “consumer thread”. The CXPACKET term came from Class E xchange Packet, and in its essence, this can be described as data rows exchanged among two parallel threads that are the part of a single process. The SQL Server CXPACKET wait type is one of the most misinterpreted wait stats. ![]()
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