Deadlock

17.7.5 Deadlocks in InnoDB A deadlock is a situation in which multiple transactions are unable to proceed because each transaction holds a lock that is needed by another one. Because all transactions involved are waiting for the same resource to become available, none of them ever releases the lock it holds. A deadlock can occur when transactions lock rows in multiple tables (through statements such as UPDATE or SELECT ... FOR UPDATE), but in the opposite order. A deadlock can also occur when such statements lock ranges of index records and gaps, with each transaction acquiring some locks but not others due to a timing issue. For a deadlock example, see Section 17.7.5.1, “An InnoDB Deadlock Example”. To reduce the possibility of deadlocks, use transactions rather than LOCK TABLES statements; keep transactions that insert or update data small enough that they do not stay open for long periods of time; when different transactions update multiple tables or large ranges of rows, use the same order of operations (such as SELECT ... FOR UPDATE) in each transaction; create indexes on the columns used in SELECT ... FOR UPDATE and UPDATE ... WHERE statements. The possibility of deadlocks is not affected by the isolation level, because the isolation level changes the behavior of read operations, while deadlocks occur because of write operations. For more information about avoiding and recovering from deadlock conditions, see Section 17.7.5.3, “How to Minimize and Handle Deadlocks”. When deadlock detection is enabled (the default) and a deadlock does occur, InnoDB detects the condition and rolls back one of the transactions (the victim). If deadlock detection is disabled using the innodb_deadlock_detect variable, InnoDB relies on the innodb_lock_wait_timeout setting to roll back transactions in case of a deadlock. Thus, even if your application logic is correct, you must still handle

Alert populates the status of each database into the DPA alerts table, and the attached script utilizes the information. If you have implemented the custom alert and named it differently than "SQL Database Offline", adjust the script as needed... 10 downloads View 6 Mar 2024 Global Deadlock Report To see a deadlock report for a single instance in DPA, drill into the instance and select the Deadlock tab on the Trends tab. This will show both a chart as well as deadlock details. However, if you want a global deadlock report across all monitored instances, the attached query will provide it. There are two results that will be output from this script: A summary table that lists each instance, the date and number of deadlocks that occurred A detail table that lists each deadlock Running... 15 downloads View 14 Feb 2024 Current Alert Status The attached script can be used to get the latest status of all alerts from the DPA repository. The result set will show the alert name, instance, latest status and last date the alert executed. This script can be executed from the DB Query Tool found in the DPA Options page or it can be executed from other query tools like SQL Server Management Studio (SSMS). 88 downloads View 29 Jan 2024 Historical Wait Times for All Instances This custom query will return historical wait time data for the specified timeframe, and y default it shows data for the last 90 days while summarizing to a daily level. This is similar data to the chart in the upper left on the Home screen, but will allow you to see more than 10 days of information. To run the query, login to the DPA repository with your favorite query tool like SSMS and execute it. To visualize

Thread/task will be highlighted in the Parallel Stacks window.Parallel Stacks SearchThe Copy Feature in Parallel StacksDid you know the Parallel Stack window offers multiple ways to copy content? You can copy specific thread information, frames, or even the entire stack trace with just a few clicks. You can share, report, or analyze the copied data outside the outside of the debugging environment.Click and CopySingle-click on the node header to select all frames in the node or double-click on a node header to select the entire stack.Hold the “Shift” key and select multiple nodes of interest, if required.Alternatively, you can also select the nodes using the right-click context menu “Select frames above/below” (above is with Task View, below is with Threads View )Now you can copy the stack information as text or image by using the shortcut keys “Ctrl+C” for copy and “Ctrl+V” for paste.Drag and copyClick and drag your mouse to select multiple nodes from the Parallel Stack Window.Now you can copy the stack information as text or image by using the shortcut keys “Ctrl+C” for copy and “Ctrl+V” for paste.To save all the contents from the parallel stack window as an image (.png), just use the Save button located at the top right of the window toolbar.Copy Feature in Parallel StacksDetecting Deadlocks with Parallel Stack’s IndicatorsHave you ever had scenarios when your multithreaded application is in a deadlock situation, and you don’t understand why you have deadlock and which threads are involved?The deadlock indicators from parallel stack windows will be the real timesavers here. It highlights all the threads that involve the deadlock and gives the big picture to understand the situation.Deadlocks Detection with Parallel Stack WindowWhen the application is in deadlock look for priority indicator icons highlighting problematic threads such as deadlock and wait scenarios .Unveiling Method Insights with the Method View!Have you ever encountered a situation where parallel stacks contain a large number of frames, making it challenging to focus on the specific method relevant to your analysis? Well, the Parallel Stack’s Method view could be your savior here, this valuable but lesser-known feature reveals the caller-callee