another session

 Use of Cursors① Cursor ConceptIn order to handle SQL statements, ORACLE must allocate a region called the context area to process the required information.This includes the number of rows to be processed, a pointer to the representation of the

View v$session_wait can be used to view the current wait events for the system and information about the resources that correspond to the wait events, thus identifying the type of bottlenecks and their objects. V$session_wait's P1, p2, and P3 tell

1 Introduction In relational databases (Db2,oracle,sybase,informix and SQL Server) the smallest recovery and transaction units are one transaction (transactions), and transactions have acid (atomicity, consistency, isolation, and permanence)

This article mainly introduces the Oracle database of temporary table usage, I hope to be helpful to everyone's study and work.One: GrammarIn Oracle, you can create the following two types of temporary tables:(1) session-specific temporary

The impact of creating an index on the execution plan Before SQL starts executing, Oracle determines the execution plan for the SQL statement and accesses the corresponding tables and indexes according to the steps of the execution plan. Once the

Sessions 1 and Session 2 cannot continue until the other party frees resources. Therefore, SQL Server chooses a session in the deadlock as the "deadlock victim." Note: The deadlock victim's session will be killed and the transaction will be rolled

A few days ago "read" "Sqlserver2005 Advanced Program Design" and "The introduction of SQL Server 2008 Programming Classic (3rd edition)," The two translations of the Chinese version of the book. found that the directory structure is roughly the

One, lck_m_s, waiting to acquire a shared lockBegins an SQL TRAN that performs an update to a data. But it is not a commit, nor a rollback.begin Tran Update [dbo]. [hr_employee] Set [Description] = ' ZZ 'In this way, the [Employee] table is locked

1. CPU Time Normal, ranked first in waiting events Num_cpu_sockets Number of physical CPUs Num_cpu_cores CPU Number of cores Num_cpus Number of logical CPUs 2. buffer busy waits (buffer busy wait/ read by other session)

Articles Locking in Microsoft SQL Server (part 12–lock escalation) Http://dba.stackexchange.com/questions/12864/what-is-lock-escalation R2 Lock escalation (Database Engine) ---Forward from Locking in Microsoft SQL Server (part 1

MySQL has three levels of Lock: page level, table level, row level.The MyISAM and memory storage engines use a table-level lock (Table-level locking), and the BDB storage engine uses a page lock (page-levelLocking), but also supports table-level

1. First create two tables, fill the Log table (User_balance_log), User Balance table (user_balance)The table structure is as follows:(1) User_balance:(2) User_balance_log:Note: The Log_type log Type 1 represents a 2 on behalf of the consumer 3 for

I. OverviewUndo saves the old data. For example, if you modify a record to modify the A-column ABC to Def, then undo holds ABC. There are two purposes: 1. If your transaction is not committed, but the column A has been modified, then someone reading

PLSQL _ performance optimization series 03_Oracle Parallel concurrency, plsql03_oracle 2014-09-25 BaoXinjian I. Summary For a large task, the general practice is to use a process for serial execution. If the system resources are sufficient, you can

OracleDatabasePessimistic lockAndOptimistic lockIs what we will introduce in this article. Sometimes, for maximum performance, databases generally have a concurrency mechanism, but the problem is Data Access conflicts. To solve this problem, most

1 StartingRedoApplyTostartapplyservicesonaphysicalstandbydatabase, ensurethephysicalstandbydatabaseisstartedandmountedandthenstartRedoApplyusingtheSQLALTERDATABASERECOVERMANAGEDSTANDBYDATABASEst atement. You 1 Starting Redo Apply To start apply

When two concurrent transactions access the same row in the database table at the same time, there may be three problems: 1,Fantasy read: Transaction T1 reads a statement that specifies the where condition and returns the result set. At this time,

Delete deletes a large table. It is not released between time and space. It is very slow because it occupies a large amount of system resources and supports rollback. The space is also occupied by this table.Truncate table Name (tablespace is

Due to the locking mechanism, when execution of a DML or DDLSQL statement is blocked, you need to find out the cause of the blocking of the SQL statement. The following describes the common diagnostic methods. Due to the lock mechanism, when

To avoid common errors in UNIX and Linux-Linux general technology-Linux technology and application information, read the following for details. Have you ever encountered an error message like Execute permission denied or The parameter list is too