how to defragment

can modify some or all of the table's partitions without losing data. The overall range of partitions before and after decomposition should be consistent.ALTER TABLE TEReorganize partition P1 into(Partition P1 values less than (+),Partition P3 values less than (+)); ----No data lossMerge partitions:Merge partition: Merge 2 partitions into one.ALTER TABLE TEReorganize partition P1,P3 into(partition P1 values less than ());----No data lossRedefine the hash partition table:Alter table EMP Partitio

statement fast operation, it is the best storage engine today! The storage engine used by default after MySQL 5.5 is InnoDBTIPS: in a production environment, if there are tables MyISAM this storage engine, it is recommended to do all MYISAM-->INNODB storage engine conversions! But after MySQL 5.7, the system tables are INNODB! 12th Palm----by six dragonsThe file system strongly recommends using XFS, no longer using EXT3,EXT4, because XFS is also the b-tree structure that is closest to the datab

Before I wrote some Android phone root security issues (see the end of the article list), in fact, I think I wrote it, today to defragment the hard disk, found a year ago wrote a piece of code, so today we will discuss together.Note: This is not about multi-NB technology, but the people who want to know about the state of the Android risk.Guide:This article describes how the so-called silent Photography is implemented (which is, of course, a malicious

during the GC, you need to reserve enough memory for the user thread to use. So the collector using the CMS is not the old age to trigger full GC, but to use the more than half (default 68%, that is, 2/3, set with-xx:cmsinitiatingoccupancyfraction), it is necessary to carry out fully GC, If the user thread consumes memory that is not particularly large, you can properly raise the-xx:cmsinitiatingoccupancyfraction to reduce the number of GC times and improve performance, if the reserved user thr

reference method, such as a reference to an object in the method area, so that the data stored by an object often contains a pointer to the method area in some form.1) A possible heap is designed to divide the heap into two parts: the reference pool and the object pool. A reference to an object is a local pointer to the reference pool. Each entry in the reference pool contains two parts: A pointer to the object data in the object pool and a pointer to the object class data in the method area. T

network layer processing. 1.2.2 Network Layer The ingress function of the IP layer is in the IP_RCV function. The function will first do a variety of checks including the package checksum, if necessary, will do IP defragment (merge multiple shards), and then packet call the pre-routing netfilter hook that has been registered, and finally arrive I The P_rcv_finish function. The Ip_rcv_finish function calls the Ip_router_input functio

cannot be overridden in a subclass.-finally: usually put in try...catch ... The subsequent construct always executes the code block, which means that the program executes either normally or unexpectedly, the code here can be executed as long as the JVM is not closed, and the code that frees the external resource is written in the finally block.-the method defined in the Finalize:object class allows the use of the Finalize () method in Java to do the necessary cleanup before the garbage collecto

,page,chunk three concepts1. Chunk is a fixed-size memory space, which defaults to 96Byte.2. The page corresponds to the actual physical space, with 1 page 1M.3. The same size of chunk is also called slab.2.1, Slab Allocation mechanism: Defragment memory for reuseThe most recent memcached by default uses a mechanism called slab Allocator to allocate and manage memory. Prior to the advent of this mechanism, the allocation of memory was performed simply

explore the topic from the answer to discuss. It is recommended that you try to answer the areas you are familiar with and discuss, and show them to the interviewer's best side.3. Can say what the new generation is doing is replication cleanup, from Survivor, to Survivor is what to do, the old age is to mark clean up, Mark clean up after the fragment to do not tidy, copy cleanup and tag cleanup have what advantages and disadvantages.Analysis: Also read the "Deep JVM virtual machine" Basic can a

Optional protocols: the NFS (Network file system) and the SMB (server Message Block)/CIFS (Common Internet file System) protocol. When configuring a file server, you will be asked to make a selection, so let's look at their differences: NFS was first developed by Sun Corporation and is the most common network file sharing protocol. NFS allows the system to share its directories and files with other systems on the network. Users and applications can access files on the remote system as