oracle commit wait

ROLLBACK:All data changes are canceled, and the data status is restored before the start of the transaction.The data lock will be released, and the locked data can be modified by all users again.Roll back to a save point:Use the SAVEPOINT statement to create a save point. If the save point name already exists, the new save point overwrites the old one.Use the rollback to savepoint statement TO roll back TO the existing storage point status. Summary:1. Data not submitted (

Tags: interval allows default insert row rebuild second Sele row detailsToday in the operation of the database, found that the data operation error, want to recover, but no transaction, supposedly, set to not default commit transaction, at this time the various operations do not respond to the database. At this point, you can rollback the transaction and undo any uncommitted changes. However, once a commit

Today, Oracle SQL plus performed the delete and query operations and then the query operations in PL/SQL. The results of the same statements were different, which made me feel quite depressed, later, I suddenly thought that the data on both sides may be inconsistent, but why is it inconsistent? It means no use of commit, I checked it on the Internet, which is probably like this: DML language, such as update

[Oracle] common wait event db file scattered read for tables that are frequently accessed, if no index is created or an appropriate index is not created, Oracle can only scan the entire table, this will cause a large number of waiting events. During full table scan, the read data is usually continuous on the disk, but the read memory is not continuous. Therefore,

Label:The so-called lock wait: is a transaction A to a data table DDL or DML operation, the system will be added to the table-level lock, when the other transaction to the table operation will wait for a commit or rollback, before you can continue the operation of B The so-called deadlock: When two or more users wait f

When you get dizzy and execute a commit, suddenly it means you're wrong, which means you and I have the same problem.Instantly feel the cold head sweating, that means you feel right. Less nonsense, here's my approach:The example below is an example of the test table.Select T.* from Test t;-----executed a bunch of commands.CommitRealize that you are wrong.It's starting to recover.SELECT * from Test as of timestamp to_timestamp (' 2016-12-29 15:04:56 ',

This is my third blog ~Today, we mainly talk about the impact of database commit on execution efficiency.Congo: When you write 800W of data, the period of commit and final commit time difference of one hours. Specific is not so I do not research, but it seems a bit reasonable ~Wangyou: Single time 50 and single difference is not small, but a single 1000 and a one

Oracle Study--oracle Wait event (5)Db File Single writeThis wait event usually occurs only in one case when Oracle updates the header information of the data file (for example, checkpoint occurs). When this wait event is obvious,

". When you execute DML (insert/update/delete), Oracle DBWR writes information to the block, including all users interested in the block status (transaction tables of interest, ITL ). To reduce the waiting time in this area, you can add initrans, which will create space in the block so that you can use multiple ITL slots. You can also add pctfree In the table where the block is located (when the number of slots created based on the specified initrans

Tags: processes PHP will also be the Principle tab pad nbsp affect spaceThis is the case for a customer in March, because after a server hardware failure, the business translation occasionally appears slow to commit. Let's take a look at the awr situation first. We can see that the load profile information for this system is actually not high, only 21 transaction per second. First Look at top5events: From the top 5event, we can find that the AVG

1.Grant Row Migration PermissionsALTER TABLE table_name enable row movement;2.To 15 minutes ago:Flashback table order to timestamp systimestamp-interval ' minute;To a point in time:FLASHBACK TABLE order to TIMESTAMP To_timestamp (' 2017-06-12 01:15:25 PM ', ' yyyy-mm-dd HH:MI:SS AM ')3. You can quickly recover after deleting a tabledrop table dbyh;Flashback table Dbyh to before drop;If the drop table has re-established a table with the same name, you need to add the Rename to clause.Flashback ta

the driver of the table in the same read data density, or increase db_cache_size; D, if the wait is in the data block, you can move the data to another block to avoid this "hot" block, add a free list in the table or use LMT tablespace; E, if the wait is in the index block, you should rebuild the index, split the index, or use the Reverse key index. To prevent buffer-related buffers from being busy waiting

) or the distance between pctused and pctfree. B. If you want to wait for the undo header block, you can add a rollback segment to solve the buffer issue; C. If you are waiting for a non-header block in the undo segment, You need to reduce the data density in the table to be read by the driver consistently, or increase DB_CACHE_SIZE; D. If the data block is waiting, move the data to another data block to avoid this "hot" data block, add a free list in

read wait event is generally 1. DB file scattered read if the database performs a full-table scan or is a full-index scan, it is common to read multiple blocks into memory (Multi block I/O), and Oracle will typically scatter these blocks in memory for performance and more efficient memory space utilization. The P3 parameter of the db file scattered Read wait

two people from updating the same data at the same time. Enqueue includes a queuing mechanism, namely, FIFO (first-in-first-out. Note: the latch mechanism of Oracle is not FIFO. Enqueue wait usually refers to St enqueue, HW enqueue, tx4 enqueue and TM enqueue.A. St enqueue is used to allocate tablespaces for space management and dictionary management. Use LMT, or try to pre-allocate the region, or at least

between pctused and pctfree.B. If you want to wait for the undo header block, you can add a rollback segment to solve the buffer issue;C. If you are waiting for a non-header block in the undo segment, You need to reduce the data density in the table to be read by the driver consistently, or increase DB_CACHE_SIZE;D. If the data block is waiting, move the data to another data block to avoid this "hot" data block, add a free list in the table, or use t

Oracle wait event-1. Knowledge about waiting events 1. The concept of waiting events from the source is introduced from ORACLE 7.0.12, with approximately 100 waiting events. In ORACLE 8.0, this number has increased to approximately 150, with approximately 220 events in ORACLE