ANBOB™

DRM is driven by the following
1.) _gc_affinity_time = Time in minutes at which statistics will be evaluated (default = 10 mins)
2.) _gc_affinity_limit = # of times a node accesses a file/object (default = 50)
3.) _gc_affinity_minimum = minimum # of times per minute a file/object is accessed before affinity kicks in
(default = 600 per minute per cpu )
4.) _lm_drm_disable = LEVEL disable drm in different level( default=0 )

Oracle RMAN was able to take incremental backups already in 9i. However, prior to introduction of Oracle 10g block change tracking (BCT), RMAN had to scan the whole datafile to and filter out the blocks that were not changed since base incremental backup and overhead or incremental backup was as high as full backup.

在使用TTS迁移一个8T 的11.2.04到19c PDB时，发现expdp和imdp元数据过程中statistic占用了约1个多小时的时间， 但是我检查了实时步骤中确实有写exclude=statistics，猜测是参数没启作用，不能忍. 结果发现这是一个预期行为

数据库会话同样会占用数据库资源，如客户端异常断开在客户端成为一个dead session会永远存在，如果客户端没有断开也没有活动就是一个idle session， 如果这个idle session做了一些修改未提交，然后下班或去吃饭、上WC、开会等，这时就会堵塞其他人对相同的数据做修改，这类会话可以叫做idle blocker session. 在自治数据库中这些session 都可以被释放或者kill / teminal 终结掉，下面对不同的session如何被释放

From 12.2, DataPump import (impdp) will always use non-parallel index creation during import overriding parameter ‘parallel’ in command line or parameter file.

无法提供摘要。这是一篇受保护的文章。

Insufficent memory related errors (i.e: ORA-27xxx).ORA-27102 error may occur because of insufficient shared memory segments.
ORA-27102: out of memory
Linux-x86_64 Error: 12: Cannot allocate memory

HW enqueue根本存在目的是为了串行化对segment高水位线的移动以及回收lob segment中的空间。造成HW enqueue contention争用的根本原因多种多样，但最终HW enqueue总是只在数据段segment High Water Mark高水位线需要移动时才被持有。

Oracle is undoing an index leaf key operation. If the key is not found, ORA-00600 [6006] is logged.
ORA-600[6006] is usually caused by a media corruption problem related to either a lost write to disk or a corruption on disk.

方法一使用了bbed修改 index key的方法， 因为表列上只有这一个索引，所以只改一个索引就可以。这里还使用相同的方法模拟ora-8102,使用第二种方法，删除bootstrap$中的index I_OBJ4 记录解决。

Sometimes due to sudden power failure and other reasons, the database data dictionary is inconsistent, such as hits ora-8102, the indexes key and the table key value does not match, often delete the index, rebuild the index can be resolved, but if the object_id <60 bootstrap$ internal The index is damaged, and the normal situation needs to be backed up and restored, because some of the indexes in these bootstrap $ cannot be rebuilt by setting event 38003

Oracle产品可从Oracle网站免费下载。但是，在使用它之前，您需要同意Oracle Technology Network（OTN）开发人员许可条款。最近几年虚拟化、云化环境的普及，Oracle的license许可有些疑惑，在这里特意整理一下。Oracle文档中关于此主题的信息确实很少，稍不注意可能会带了百万级的费用消耗, 前提是你有严格对待ORACLE的软件许可，当然还是以Oracle合同中指定条款为主。

是否遇到过在分析AWR报告时，明明AAS很高，但从Top 10 Foreground Events by Total Wait Time 上看top event使用的百分比加起来离100%很远？ 那DB TIME去哪了？下面我附一个11G(11.2.0.4 RAC on AIX) AWR 案例，这个问题在12c的AWR中提供了TOP EVENT。

执行计划中的谓词信息非常的重要，有助于我们判断是否进行了隐式转换，为什么没有使用索引等， 使用dbms_xplan.display_cursor可以从shared_pool中取到sq cursor的谓词，但是在20c之前dbms_xplan.display_AWR 在之前的版本中并不能， 但是Oracle社区的投票和诸多人的推动下，终于在oracle 20c所谓词信息也在dbms_xplan.display_AWR中显示

前几日同事那遇到的灾难性的SQL, 一个简单的子查询，不知是一开始就写错了子查询中的列名，还是子查询的表后期有改列名，导致主查询表所有数据被更改，在未指定列所属表名时，列的查询顺序先检查子查询再检查主查询，这是oracle的预期行为，并不会报列不存在，只是在后期书写时子查询记的增加列上的所属别名。

Wait for Table Lock
Meaning:
Wait for exclusive TM enqueue in materialized view operations.

Oracle 11.2.0.3 2nodes RAC on AIX, node1 DB instance crash and db alert log show “ORA-00600 [ORA_NPI_ERROR] ORA-00600: internal error code [kffilCreate01]” and “ORA-15064: communication failure with ASM instance” then Instance terminated by ASMB.

Oracle database use DDL statements to define structures such as tables to store data and functions to store code. By default Oracle database does not log any DDL operations performed by any user.When someone do some destructive DDL in DB, we often need the DDL log..In this article I will only record the method of using Oracle Database Lifecycle Management Pack( Enable_ddl_logging)

叕一个oracle 12c频繁生成日志文件的问题，最近一套12.2的RAC突然又文件系统告警，生成了大量的trace文件，db alert log也在不停的显示如下内容：
ADVISORY: Please collect redo for investigation of ORA-8103. Use command:
ALTER SYSTEM DUMP REDO scn min 1 scn max 16716635042430 dba min 32 2094058 dba max 32 2094058;

The following errors have recently occurred in our database( Oracle 19c RAC):
ORA-01578: ORACLE data block corrupted (file # xxx, block # yyyyy)
ORA-01110: data file xxx: ‘xxxxxxxxxxxxxxxxx.dbf’
ORA-26040: Data block was loaded using the NOLOGGING option