ORACLE time model （ORACLE 时间模型）

V$SESS_TIME_MODEL

V$SESS_TIME_MODEL

displays the session-accumulated time for various operations. The time reported is the total elapsed or CPU time (in microseconds). Any timed operation will buffer at most 5 seconds of time data. Specifically,
this means that if a timed operation (such as SQL execution) takes a long period of time to perform, the data published to this view is at most missing 5 seconds of the time accumulated for the operation.
The time values are 8-byte integers and can therefore hold approximately 580,000 years of time before wrapping. Background process time is not included in a statistic value unless the statistic is specifically for background processes.

Column	Datatype	Description
SID	NUMBER	Session ID (same as in V$SESSION )
STAT_ID	NUMBER	Statistic identifier for the time statistic
STAT_NAME	VARCHAR2(64)	Name of the statistic (see Table 9-1)
VALUE	NUMBER	Amount of time (in microseconds) that the session has spent in this operation

Table 9-1 V$SESS_TIME_MODEL and V$SYS_TIME_MODEL Statistics

Statistic Name	Description
DB Time	Amount of elapsed time (in microseconds) spent performing Database user-level calls. This does not include the elapsed time spent on instance background processes such as PMON. 数据库执行用户层级调用的时间（微秒级），不包含后台进程的时间
DB CPU	Amount of CPU time (in microseconds) spent on database user-level calls. This does not include the CPU time spent on instance background processes such as PMON. 数据库执行用户层级调用的CPU时间，不包括后台进程时间
background elapsed time	Amount of elapsed time (in microseconds) consumed by database background processes. 花费在后台进程上的时间
background CPU time	Amount of CPU time (in microseconds) consumed by database background processes. 花费在后台进程的CPU时间
sequence load elapsed time	Amount of elapsed time spent getting the next sequence number from the data dictionary. 花费在从数据字典获取下一序列值上的时间。 If a sequence is cached, then this is the amount of time spent replenishing the cache when it runs out. No time is charged when a sequence number is found in the cache. 如果序列已经被cache，那么此时间为当序列用光后，补充cache的时间 For non-cached sequences, some time will be charged for every nextval call. 对于非cached 的序列，每次获取都会增加此时间。
parse time elapsed	Amount of elapsed time spent parsing SQL statements. It includes both soft and hard parse time. 用于解析SQL语句的时间，包含软硬解析。
hard parse elapsed time	Amount of elapsed time spent hard parsing SQL statements. 硬解析时间
SQL execute elapsed time	Amount of elapsed time SQL statements are executing. Note that for select statements this also includes the amount of time spent performing fetches of query results. SQL语句执行时间。注意select 语句包含获取返回结果的时间
connection management call elapsed time	Amount of elapsed time spent performing session connect and disconnect calls. 花费在session连接与断开的时间
failed parse elapsed time	Amount of time spent performing SQL parses which ultimately fail with some parse error. 最终解析失败的时间
failed parse (out of shared memory) elapsed time	Amount of time spent performing SQL parses which ultimately fail with error ORA-04031 . 由于4031错误，导致最终解析失败所花费的时间。
hard parse (sharing criteria) elapsed time	Amount of elapsed time spent performing SQL hard parses when the hard parse resulted from not being able to share an existing cursor in the SQL cache. 由于不能共享现有游标，产生硬解析的时间
hard parse (bind mismatch) elapsed time	Amount of elapsed time spent performing SQL hard parses when the hard parse resulted from bind type or bind size mismatch with an existing cursor in the SQL cache. 由于绑定变量类型或者大小导致不能共享现有游标，产生硬解析的时间
PL/SQL execution elapsed time	Amount of elapsed time spent running the PL/SQL interpreter. This does not include time spent recursively executing/parsing SQL statements or time spent recursively executing the Java VM. 执行PL/SQL花费的时间。不包含递归执行或解析SQL语句的时间，也不薄或在jvm中执行的时间，
PL/SQL compilation elapsed time	Amount of elapsed time spent running the PL/SQL compiler. PL/SQL编译器花费的时间
inbound PL/SQL rpc elapsed time	Time inbound PL/SQL remote procedure calls have spent executing. It includes all time spent recursively executing SQL and JAVA, and therefore is not easily related to "PL/SQL execution elapsed time". 远程存储过程调用花费的时间。包含递归执行SQL和java。因此不能简单的与“PL/SQL execution elapsed time".相关联
Java execution elapsed time	Amount of elapsed time spent running the Java VM. This does not include time spent recursively executing/parsing SQL statements or time spent recursively executing PL/SQL. 在JVM中花费的时间。不包含SQL与PL/SQL递归执行或解析的时间。
RMAN cpu time (backup/restore)	Amount of CPU time (in microseconds) spent in RMAN backup and restore operations. rman 备份恢复花费的时间
repeated bind elapsed time	Amount of elapsed time spent giving new values to bind variables (rebinding). 为绑定变量赋予新值的时间（重新绑定）

The relationships between the statistics listed in Table 9-1 form two trees in which all the time reported by a child in the
tree is contained within the parent in the tree. The following are the relationship trees; the number is the level in the given tree.

1) background elapsed time
2) background cpu time
3) RMAN cpu time (backup/restore)
1) DB time
2) DB CPU
2) connection management call elapsed time
2) sequence load elapsed time
2) sql execute elapsed time
2) parse time elapsed
3) hard parse elapsed time
4) hard parse (sharing criteria) elapsed time
5) hard parse (bind mismatch) elapsed time
3) failed parse elapsed time
4) failed parse (out of shared memory) elapsed time
2) PL/SQL execution elapsed time
2) inbound PL/SQL rpc elapsed time
2) PL/SQL compilation elapsed time
2) Java execution elapsed time
2) repeated bind elapsed time

The relationship between a parent and a child in the tree indicates containment only. Keep the following in mind with regard to the tree:

Children do not necessarily add up to the parent.

Children are not necessarily exclusive (that is, it is possible that they overlap).

The union of children does not necessarily cover the whole of the parent.