EBS R12.2 Online Patching(ADOP)及Oracle EBR - 1

1.  Does Online Patching require the 11gR2 Oracle Database Edition Based Redefinition (EBR) feature?
     Yes. Online patching depends on the Edition Based Redefinition (EBR) feature that was introduced in the Oracle

11gR2 Database. Most notably, EBR allows editioning of code objects in the database. To do this, it provides new object types such as

editions, editioning views, and cross-edition triggers, all of which are part of the Online Patching infrastructure.

2.  What are the phases that make up the Online Patching cycle?  
打補丁的各個階段是可以分開實施的， CUTOVER可以在閒時再執行 (命令如adop phase=cutover)
 The Online Patching cycle consists of the following phases:
1.  Prepare a virtual copy (patch edition) of the running application (run edition).
2.  Apply patches to the patch edition of the application.
3.  Finalize the system in readiness for the cutover phase.
4.  Cutover to the patch edition and make it the new run edition.
5.  Cleanup obsolete definitions or data to recover space.

3.  What downtime is required during an Online Patching cycle?  
The cutover phase requires a short period of downtime (typically a few minutes) for transition tasks such as a restart of the application tier services.
Cutover切換階段需要停服務幾分鐘。這裡是切換patch fs 與 runtime fs, 而不是同步，兩個file system同步要到下次

prepare階段。 兩個file system是不能同時執行的  ( Cutover先切換db edition然後是app file system)。

Once an online patch is applied, services must be started from the right RUN File system only. Both the file systems are not equal any more. ADOP manages the file sync, creating editions, etc and finally invokes adpatch to patch the PATCH environment.   ADOP always patches the  $PATCH_BASE, while application is running out of $RUN_BASE.    Once patching $PATCH_BASE is complete, we need to flip $PATCH_BASE into $RUN_BASE and $RUN_BASE into  $PATCH_BASE. This is known as cutover phase in ADOP. This still needs downtime/outage.

Cutover Phase包含一下過程 ：
 1.Finalize   (cutover也包括了finalize phase, 提前進行finalize可以節省cutover的時間)
 2.Application Tier Services Switch
 3.Database Cutover
 4.File System Cutover
 5.Retire Old Editions
 6.Terminate Old Database Sessions
 7.Application Tier Services Switch

       因為資料庫表的特殊性(size過大，不像應用code那麼小)，所以需要在cutover之前進行同步 (同步指的是runtime版本的table
中的變化資料透過trigger同步到patch版本的table中，反過來，patch apply帶來的變更僅僅在patch版本的table中進行，不會同步
實施到runtime版本的table)， 不像APP兩套file system，patch apply期間不同步, 到了Cutover 階段再進行交換 。