apache openoffice writer page 1 starts on page 4

#Apache openoffice writer page 1 starts on page 4 how to#

This can cause such a query to exceed the lock escalation thresholds.

This means that what may look like a SELECT statement at a 'read-committed' isolation level might acquire many thousands of key locks (on both the clustered index and one nonclustered index). If SQL Server does use PREFETCH for a bookmark lookup, it must increase the transaction isolation level of a portion of the query to 'repeatable read' for a portion of the query. If SQL Server estimates that a Bookmark Lookup logical operator will return many rows, it might use a PREFETCH clause to do the bookmark lookup. One goal of this optimization is to make index seeks return as few rows as possible to minimize the cost of bookmark lookups (maximize the selectivity of the index for the query). For more information, see SQL Server Index Architecture and Design Guide. Review the execution plan and potentially create new nonclustered indexes to improve query performance. After you identify that the query that causes lock escalation, look for opportunities to create new indexes or to add columns to an existing index to remove index or table scans and to maximize the efficiency of index seeks. Additionally, these increase the chance of deadlocks, and adversely affect concurrency and performance. Large scans or many bookmark lookups can increase the chance of lock escalation. Reduce the query's lock footprint by making the query as efficient as possible. For example, you run the following query: DECLARE bit = 0 ĭELETE TOP(1000) FROM LogMessages WHERE LogDate < '20020102' For example, you run the following query to remove 100,000+ old records from an audit table, and then you determine that the query caused a lock escalation that blocked other users: DELETE FROM LogMessages WHERE LogDate < '20020102' īy removing these records a few hundred at a time, you can dramatically reduce the number of locks that accumulate per transaction. There are several methods to achieve this goal, including the following strategies:īreak up large batch operations into several smaller operations. The simplest and safest method to prevent lock escalation is to keep transactions short and reduce the lock footprint of expensive queries so that the lock escalation thresholds are not exceeded. If your blocking problems are not caused by lock escalation, see the INF: Understanding and resolving SQL Server blocking problems troubleshooting steps. In particular, if the TAB lock is an intent lock (such as a lock mode of IS, IU, or IX), this isn't caused by lock escalation. If the lock that's blocking other users is anything other than a TAB (table-level) lock that has a lock mode of S (shared), or X (exclusive), lock escalation isn't the problem.

#Apache openoffice writer page 1 starts on page 4 how to#

If lock escalation is occurring, verify that the escalated table lock is blocking other users.įor more information about how to identify the head blocker and the lock resource that's held by the head blocker and that's blocking other server process IDs (SPIDs), see INF: Understanding and resolving SQL Server blocking problems. If you don't see any lock_escalation events, lock escalation isn't occurring on your server, and the information in this article doesn't apply to your situation.

To determine whether lock escalation is occurring at or near the time when you experience blocking issues, start an Extended Events session that includes the lock_escalation event. Lock escalation doesn't cause most blocking problems. Original product version: SQL Server Original KB number: 323630 Determine whether lock escalation is causing blocking This article discusses how to determine whether lock escalation is causing blocking and how to deal with undesirable lock escalation. However, some application or query designs might trigger lock escalation at a time when this action not desirable, and the escalated table lock might block other users. Typically, SQL Server's default behavior causes lock escalation to occur only at those times when it would improve performance or when you must reduce excessive system lock memory to a more reasonable level. When it makes this decision, SQL Server considers the number of locks that are held on a particular scan, the number of locks that are held by the whole transaction, and the memory that's used for locks in the system as a whole. Microsoft SQL Server dynamically determines when to do lock escalation.

Lock escalation is the process of converting many fine-grained locks (such as row or page locks) to table locks.