db2 locks

operation is very large, it will lead to competition for logs, resulting in very slow operations. If you insert, update, or delete a table without logs, the log is rarely used. However, if the operation fails, the table cannot be rolled back. Therefore, the consistency is not guaranteed and the table can only be deleted and rebuilt. 4) Create Table-level locks for tables to minimize the number of locks. Be

. Supported files include ixf and del. Db2 "export to fileName. del of del select * from tableName" // db2 imports table data to a file Db2 "import from fileName. del of del insert into tableName" // import the data in the file to the table in db2 4. Check whether the table exists in

-forward process started:Db2=>rollforward database Db2cert Query status]9. Report information about all the recovery history files in the database Db2cert:Db2=>list History all for Db2cert10. Modify the configuration of the database manager, and the SQL information in the application that accesses all databases for this instance is captured:Db2=>update dbm configuration using dft_mon_stmt on11. SQL information for the application capturing the activation switch:Db2=>update monitor switches using

manages resources and locks, SQL Server not only manages locks, You also manage compatibility or escalation locking between lockdown modes and resolve deadlock issues. With SQL Server's powerful, granular locking mechanism, concurrency performance is maximized, but using as few system resources as possible is what we want most. There are two kinds of locking system: One is locking the shared data, which is

Differences between semaphores and spin locks The spin lock does not cause the caller to sleep.If the spin lock has been maintained by another execution unit, the caller will keep repeating to check whether the lock holder has released the lock. "Spin" means "in situ ".The semaphore causes the caller to sleep.It will drag the process out of the running queue unless the lock is obtained. ------------------------------------------------------Although th

DB2 obtains detailed information about the current user table, field, index, and so on. db2 current user Obtain detailed information about all tables, fields, and indexes. SELECT d. name tbName, COALESCE (d. remarks, '') tbDesc,. name columnName,. coltype columnType, decode (. nulls, 'y', '1', '0') notNull, decode (. identity, 'y', '1', '0') auto,. longlength width,. scale precision, COALESCE (. remarks,

Label:Connect reset should terminate the database connection with a commit action terminate should be able to terminate this client-initiated process and release resources Terminate is a command, in addition to disconnecting, it also terminates the CLP (command line processor) background process, which is the common db2bp.connect reset is the SQL statement quit Exit CLP, but the database connection is constantly open connect reset disconnects the database but does not exit the CLPterminate

', 5, ' S/row-x (SSX) ', 6, ' Exclusive ', To_char (Lmode)) Mode_held, DECODE (REQUEST, 0, ' None ', 1, ' Null ', 2, ' Row-s (S) S) ', 3, ' Row-x (SX) ', 4, ' Share ', 5, ' S/row-x (SSX) ', 6, ' Exclusive ', To_char (REQUEST)) mode_requested, o.owner| | | o.object_name| | ' ('|| o.object_type| | ') ', S.type Lock_type, L.id1 lock_id1, L.id2 lock_id2 from V$lock L, SYS. Dba_objects O, v$session S WHERE l.sid = s.sid and l.id1 = o.object_id DB2 can act

In the actual production environment, if the concurrency is not large, you can use the pessimistic locking method. This method is very convenient and simple to use. However, if the system concurrency is very large, pessimistic locking will bring about a very large performance problem, so we need to choose an Optimistic Locking method. Pessimistic locks assume that other users attempt to access or change the objects you are accessing and changing have

How to Use locks intelligentlyTips for using locks efficiently in Java Document options Valign = "TOP"> Width = "122">

protected dataOther users can still access the service normally, such as deleting and updating the service. Therefore, although the above two methods can ultimately achieve this requirement, it will greatly affect otherThe user's normal use. Therefore, these two methods are not recommended by the author. I recommend that you use row-level locks. Next I will elaborate on this method in detail, with special emphasis onMeaning. For example, there are tw

The DB2 isolation level described below is the Repeatable read level. As one of the important DB2 isolation levels, you can use the Repeatable read, it is impossible to lose updates and access unimplemented data and phantom rows. Repeatable read Repeatable read RR) locks all rows referenced by the application in the work unit. With "repeatable", an application in

Lock mechanism series for SQL Server:lock mechanism for SQL Server (i)--Overview (types and scopes of locks)lock mechanism for SQL Server (ii)--Overview (lock compatibility and resources that can be locked)lock mechanism for SQL Server (iii)--Overview (Locks and transaction isolation levels)lock mechanism for SQL Server (iv)--Overview (impact of various transaction isolation levels)Lock: Popular speaking is

multi-granularity blocking mechanism with intention locks to control concurrency and ensure data consistency. Its DML lock (Data lock) is divided into two levels (granularity): Table-level and row-level. Generally, DML operations only obtain the intention lock (RS or RX) at the table level, and the real blocking granularity is still at the row level; DB2 also uses a multi-granularity blocking mechanism wit

Read/write locks in Java concurrent packages and their Implementation Analysis 1. Preface Usually used locks such as ReentrantLock in Java concurrent packages are usually exclusive locks. These locks can be accessed by only one thread at a time, the read and write locks can

* from tableName" // db2 imports table data to a file Db2 "import from fileName. del of del insert into tableName" // import the data in the file to the table in db2 4. Check whether the table exists in DB2 select*from"SYSIBM"."SYSTABLES"wherelower(name)='afa_maintransdtl' 5. Solve the

also affect the system performance. Simultaneous operations by multiple users may result in data inconsistency. To prevent data loss and access to uncommitted data due to simultaneous modifications, and to protect read data, DB2, use the Lock mechanism to implement control. DB2 can lock table spaces, tables, columns, and indexes. The larger the lock granularity, the simpler the lock, the smaller the overhe

Serialization (Serializable): lowest performance, range lock causes concurrency degradation Snapshot (snopshot): This is done by creating an additional copy in tempdb to avoid dirty reads, non-repeatable reads, which can impose additional burdens on tempdb Mode of Lock shared lock (S lock): used to read the lock added by the resource. A resource that has a shared lock cannot be modified. Shared locks are read by de

1ObjectiveThe database large concurrency operation takes into account the deadlock and lock performance issues. See online most vague (especially update lock), so here is a concise explanation, for the following description of the convenient, here with T1 for a database execution request, T2 represents another request, can also be understood as T1 a thread, T2 for another thread. T3,t4 and so on. The following is an example of SQL Server (2005).2Types of Loc