提交读，未提交读，可重复读，可串行读。
Read committed, Read uncommitted, Repeatable Read, Serializable.
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。
For example, reading from a read - only look up table doesn t require repeatable read, and uncommitted read is sufficient.
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。
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.
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)。
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)。
Supports table and row level locking and 4 isolation levels, RR (repeatable read), rs (read stability), CS (default - cursor stability) and ur (uncommitted read).
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