Oracle process和sessions 解釋

session:

Because every login requires a session, this parameter effectively determines the maximum number of concurrent users in the system. You should always set this parameter explicitly to a value equivalent to your estimate of the maximum number of concurrent users, plus the number of background processes, plus approximately 10% for recursive sessions.

12c (1.5 * PROCESSES) + 22

ALTER SYSTEM can be used in a PDB only to change the value of the SESSIONS parameter for that PDB. (僅限在PDB中修改)

For a CDB, the root container's SESSIONS parameter specifies the total number of sessions for the database.
the SESSIONS parameter does not count recursive sessions and hence does not require the 10% adjustment.

process --- 針對(duì)的操作系統(tǒng)進(jìn)程(這里不做詳述，專(zhuān)屬和共享模式)，而session是db層，兩個(gè)概念不同。

這里涉及到的試圖有：(其中概念可以查看官檔)

gv$session
gv$process
v$resource_limit
v$license

---這里有個(gè)捷徑提醒下，修改這個(gè)參數(shù)一般人會(huì)重啟cdb，但是其實(shí)可以在某個(gè)節(jié)點(diǎn)修改sessions，然后shutdown immediate(當(dāng)然要快速生效也可以shutdown abort)其中一個(gè)cdb節(jié)點(diǎn)，然后startup，同樣可以生效，但是記得要在把這個(gè)節(jié)點(diǎn)運(yùn)行的service要start。