was宕機(jī)常見(jiàn)問(wèn)題及參考解決方案-資料下載頁(yè)
2025-06-05 19:42本頁(yè)面
【正文】 to make connection pooling work most efficiently and to prevent problems. One of the most important practices is to always call close() on a connection object as soon as the application finishes using it. This is necessary so that the connection can return to the free connection pool. Care should be taken to make sure connections are closed even in exception condition. Failing to close connections means that connections are leaked, reducing the number of connections available in the connection pool, and leading to ConnectionWaitTimeoutExceptions. 收集日志：To enable connection leak diagnostics, set the Log Detail Level to “ConnLeakLogic=finest” and enable diagnostic tracing. 分析工具：Tivoli Performance Viewer應(yīng)對(duì)策略：找到連接沒(méi)有關(guān)閉的地方，將其關(guān)閉。連接長(zhǎng)時(shí)間被占用（LTC Connection Occupation）典型表現(xiàn)：盡管數(shù)據(jù)庫(kù)SQL語(yǔ)句執(zhí)行很快，但 SERVLET/JSP 本身仍未完成，則這個(gè)數(shù)據(jù)庫(kù)連接依然對(duì)其它線程失效，標(biāo)記為不可使用。所以說(shuō)，如果有很多長(zhǎng)時(shí)間的SERVLET/JSP，應(yīng)該排隊(duì)挨個(gè)處理。When a servlet/jsp is invoked, the Web container in WebSphere Application Server automatically creates an LTC context. When a connection is obtained in an LTC, the default behavior is that the connection does not return to the free pool until the LTC ends. The LTC does not end until the servlet/jsp pletes. If the servlet/jsp performs a longrunning task, the connection may remain allocated to the application for a long period of time. The effect of this is that the connection is leaked. When many connections are leaked, ConnectionWaitTimeoutExceptions may occur.This functionality makes it easy for you to find the method responsible for connection leaks by printing the stack traces for all open database connections whenever a thread throws an exception because it couldn’t get a database connection from the pool in a reasonable amount of time. 應(yīng)對(duì)策略：長(zhǎng)時(shí)間不能處理完成的SERVLET/JSP，最好不要并發(fā)進(jìn)行，應(yīng)排隊(duì)執(zhí)行。或者增加最大數(shù)據(jù)庫(kù)連接數(shù)。死鎖（Dead Lock）數(shù)據(jù)庫(kù)連接也是一種資源，如果有某線程同時(shí)要用到多個(gè)數(shù)據(jù)庫(kù)連接，但是在申請(qǐng)數(shù)據(jù)庫(kù)連接的時(shí)候不是一次性的獲取所有數(shù)據(jù)庫(kù)連接資源，從而導(dǎo)致互相等待，發(fā)生有資源搶占死鎖的問(wèn)題。應(yīng)對(duì)策略：增加最大的數(shù)據(jù)庫(kù)連接數(shù)，或者調(diào)整程序，不要使用此種模式。
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