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有时，人与人之间不能有效沟通，很可能是大家没有一个统一的概念库。
甚至是，我们说着很多时髦的话，却不一定真正理解自己说的话，因为我们连基本的概念都没弄懂或者一知半解。
| latch sleeping | 闩锁休眠 | The phenomenon that occurs when a process releases the CPU before renewing the latch request. |
| latch spinning | 闩锁自旋 | The phenomenon that occurs when a process repeatedly requests a latch in a loop. |
| leaf block | 叶块 | In a B-tree index, a lower-level block that stores index entries. The upper-level branch blocks of a B-tree index contain index data that points to lower-level index blocks. |
| left outer join | 左外连接 | The result of a left outer join for table A and B contains all records of the left table A, even if the join condition does not match a record in the right table B. For example, if you perform a left outer join of employees (left) to departments (right), and if some employees are not in a department, then the query returns rows from employees with no matches in departments. |
| library cache | 库缓存 | An area of memory in the shared pool. This cache includes the shared SQL areas, private SQL areas (in a shared server configuration), PL/SQL procedures and packages, and control structures such as locks and library cache handles. |
| list partitioning | 列表分区 | In partitioning strategy that uses a list of discrete values as the partition key for each partition. You can use list partitioning to control how individual rows map to specific partitions. By using lists, you can group and organize related sets of data when the key used to identify them is not conveniently ordered. |
| listener | 监听程序 (listener) | A process that listens for incoming client connection requests and manages network traffic to the database. |
| listener registration process | 监听程序注册进程 | The process that registers information about the database instance and dispatcher processes with the Oracle Net listener. |
| literal | 立即数（字面值） | A fixed data value. |
| LOB (Large object) | 大对象 | Large Objects include the following SQL datatypes: BLOB, CLOB, NCLOB, and BFILE. These datatypes are designed for storing data that is large in size. |
| local partitioned index | 本地分区索引 | An index partitioned on the same columns, with the same number of partitions and the same partition bounds as its table. A one-to-one parity exists between index partitions and table partitions. |
| local role | 本地角色 | In a CDB, a role that exists only in a single PDB, just as a role in a non-CDB exists only in the non-CDB. Unlike a common role, a local role may only contain roles and privileges that apply within the container in which the role exists. |
| local user | 本地用户 | In a multitenant container database (CDB), any user that is not a common user. |
| locale | 语言环境 (locale) | Within the context of globalization support, a linguistic and cultural environment in which a system or program is running. |
| locally managed tablespace | 本地管理的表空间 | A tablespace that uses a bitmap stored in each data file to manage the extents. In contrast, a dictionary-managed tablespace uses the data dictionary to manage space. |
| lock | 锁定 | A database mechanism that prevents destructive interaction between transactions accessing a shared resource such as a table, row, or system object not visible to users. The main categories of locks are DML locks, DDL locks, and latches and internal locks. |
| lock conversion | 锁转换 | The automatic conversion of a table lock of lower restrictiveness to one of higher restrictiveness. For example, suppose a transaction issues a SELECT ... FOR UPDATE for an employee and later updates the locked row. In this case, the database automatically converts the row share table lock to a row exclusive table lock. |
| lock escalation | 锁升级（Oracle中不允许） | A situation that occurs in some databases when numerous locks are held at one level of granularity (for example, rows) and the database raises the locks to a higher level of granularity (for example, table). Oracle Database never escalates locks. |
| log sequence number | 日志序列号 | A number that uniquely identifies a set of redo records in a redo log file. When the database fills one online redo log file and switches to a different one, the database automatically assigns the new file a log sequence number. |
| log switch | 日志切换 | The point at which the log writer process (LGWR) stops writing to the active redo log file and switches to the next available redo log file. LGWR switches when either the active redo log file is filled with redo records or a switch is manually initiated. |
| LGWR (log writer process) | LGWR (日志写入程序进程) | The background process responsible for redo log buffer management—writing the redo log buffer to the online redo log. LGWR writes all redo entries that have been copied into the buffer since the last time it wrote. |
| logical I/O | 逻辑I/O | Reads and writes of buffers in the database buffer cache. |
| logical read | 逻辑读 | A read of a buffer in the database buffer cache. |
| logical rowid | 逻辑rowid | A rowid for an index-organized table. A logical rowid is a base64-encoded representation of a table primary key. |
| logical transaction ID | 逻辑事务ID | A globally unique identifier that defines a transaction from the application perspective. The logical transaction ID is bound to the database transaction ID. |
| logical volume | 逻辑卷 | A virtual disk partition. |
| LVM (logical volume manager) | LVM（逻辑卷管理程序） | A software package, available with most operating systems, that enables pieces of multiple physical disks to be combined into a single contiguous address space that appears as one disk to higher layers of software. |
| lookup table | 查询表 | A table containing a code column and an associated value column. For example, a job code corresponds to a job name. In contrast to a master table in a pair of master-detail tables, a lookup table is not the means to obtain a detailed result set, such as a list of employees. Rather, a user queries a table such as employees for an employee list and then joins the result set to the lookup table. |
| lost update | 更新丢失 | A data integrity problem in which one writer of data overwrites the changes of a different writer modifying the same data. |
| MMON (manageability monitor process) | MMON （可管理性监控进程） | The background process that performs many tasks related to the Automatic Workload Repository (AWR). For example, MMON writes when a metric violates its threshold value, taking snapshots, and capturing statistics value for recently modified SQL objects. |
| mantissa | 浮点数的有效数字部分 | The part of a floating-point number that contains its significant digits. |
| MSSM (manual segment space management) | MSSM（手动段空间管理） | A legacy space management method that uses a linked list called a free list to manage free space in a segment. |
| manual undo management mode | 手动撤销管理模式 | A mode of the database in which undo blocks are stored in user-managed undo segments. In automatic undo management mode, undo blocks are stored in a system-managed, dedicated undo tablespaces. |
| master database | 主数据库 | In replication, the source of the data that is copied to a subscriber database. The replication agent on the master database reads the records from the transaction log for the master database. It forwards changes to replicated elements to the replication agent on the subscriber database. The replication agent on the subscriber database then applies the updates. |
| master-detail tables | 主-子表 | A detail table has a foreign key relationship with a master table. For example, the employees detail table has a foreign key to the departments master table. Unlike a lookup table, a master table is typically queried and then joined to the detail table. For example, a user may query a department in the departments table and then use this result to find the employees in this department. |
| master site | 主站点 | In a replication environment, a different database with which a materialized view shares data. |
| master table | 主表 | In a replication environment, the table associated with a materialized view at a master site. |
| materialized view | 物化视图 | A schema object that stores the result of a query. Oracle materialized views can be read-only or updatable. See also view. |
| media recovery | 介质恢复 | The application of redo or incremental backups to a data block or backup data file. |
| metadata link | 元数据链接 | In a PDB, an internal mechanism that points to a dictionary object definition stored in the root. For example, the OBJ$ table in each PDB uses a metadata link to point to the definition of OBJ$ stored in the root. |