In fact, the only row-level locking that remains during INSERT is the next-key locks that are required to protect an INSERT from adding keys to repeatable read scanners.
实际上，在INSERT期间惟一保持的行级锁是next - key锁，这个锁用于使INSERT不会添加键到可重复的读扫描器。
Supports table and row level locking and 4 isolation levels, RR (repeatable read), rs (read stability), CS (default - cursor stability) and ur (uncommitted read).
支持表级和行级锁以及4个隔离级别：RR(可重复读)、RS(读可靠)、CS(默认——游标可靠)和UR(未提交读)。
With the "Repeatable Read" data region fetch requests issued multiple times within the same transaction will always produce the same result yielding better application throughput.
在相同事务下对“可重复读取”区域内数据的多次请求的结果是相同的，但能够带来更好的应用吞吐量。
Repeatable read — the transaction always reads the same data during the transaction.
Repeatable read(可重读)——在事务过程中，事务始终读取相同的数据。
However, for entity beans this rule has to be relaxed; due to the nature of the model, most pessimistic locking access intents require at least Repeatable Read.
但是，对于实体Bean则可不遵循此规则，由于该模型本身的特性，多数悲观锁定访问都需要至少Repeatable Read。
These next key locks are only obtained when the key INSERT finds that a scanner with a Repeatable Read (RR) isolation level has a row lock on the next-higher key in the index.
这些nextkey锁只有在keyINSERT发现带有Repeatable Read (RR)隔离级别的扫描器在索引中的next -higher键上有一个行锁时才能获得。
For example, reading from a read - only look up table doesn t require repeatable read, and uncommitted read is sufficient.
比如，读取只读的查找表不需要可重复读级别，未提交读级别就足够了。
Read committed, Read uncommitted, Repeatable Read, Serializable.
提交读，未提交读，可重复读，可串行读。
Read committed, Read uncommitted, Repeatable Read, Serializable.
提交读，未提交读，可重复读，可串行读。
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