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关于数据库open的深入探究

答案:关于数据库open的深入探究

  SQL> shutdown immediate

  Database closed.

  Database dismounted.

  ORACLE instance shut down.

  SQL> startup mount

  ORACLE instance started.

  Total System Global Area 131142648 bytes

  Fixed Size 451576 bytes

  Variable Size 104857600 bytes

  Database Buffers 25165824 bytes

  Redo Buffers 667648 bytes

  Database mounted.

  SQL> alter session set sql_trace = true;

  Session altered.

  SQL> alter database open;

  Database altered.

  SQL>

  首先我们来参考跟踪文件的前部分(参考附件)

  这是第一个对象的创建

  create table bootstrap$ ( line# number not null, obj#

  number not null, sql_text varchar2(4000) not null) storage (initial

  50K objno 56 extents (file 1 block 377))

  接下来我们来看执行的是

  select line#, sql_text

  from

  bootstrap$ where obj# != :1

  (这里实际上是逐步提取内容建立字典表本身的结构,根据后面内容可知)

  那么在这里我们在数据库中来看看 bootstap$

  SQL> desc bootstrap$

  Name Null? Type

  ----------------------------------------- -------- ----------------------------

  LINE# NOT NULL NUMBER

  OBJ# NOT NULL NUMBER

  SQL_TEXT NOT NULL VARCHAR2(4000)

  SQL>

  SQL> select count(*) from bootstrap$;

  57

  SQL>

  SQL> select obj#,sql_text from bootstrap$ where rownum<11;

  -1

  8.0.0.0.0

  0

  CREATE ROLLBACK SEGMENT SYSTEM STORAGE ( INITIAL 112K NEXT 1024K MINEXTENTS 1 M

  AXEXTENTS 32765 OBJNO 0 EXTENTS (FILE 1 BLOCK 9))

  8

  CREATE CLUSTER C_FILE#_BLOCK#("TS#" NUMBER,"SEGFILE#" NUMBER,"SEGBLOCK#" NUMBER)

  PCTFREE 10 PCTUSED 40 INITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 24K NEXT 1024K

  MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 8 EXTENTS (FILE 1 BLOCK

  73)) SIZE 225

  9

  CREATE INDEX I_FILE#_BLOCK# ON CLUSTER C_FILE#_BLOCK# PCTFREE 10 INITRANS 2 MAXT

  RANS 255 STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PC

  TINCREASE 0 OBJNO 9 EXTENTS (FILE 1 BLOCK 81))

  14

  CREATE TABLE SEG$("FILE#" NUMBER NOT NULL,"BLOCK#" NUMBER NOT NULL,"TYPE#" NUMBE

  R NOT NULL,"TS#" NUMBER NOT NULL,"BLOCKS" NUMBER NOT NULL,"EXTENTS" NUMBER NOT N

  ULL,"INIEXTS" NUMBER NOT NULL,"MINEXTS" NUMBER NOT NULL,"MAXEXTS" NUMBER NOT NUL

  L,"EXTSIZE" NUMBER NOT NULL,"EXTPCT" NUMBER NOT NULL,"USER#" NUMBER NOT NULL,"LI

  STS" NUMBER,"GROUPS" NUMBER,"BITMAPRANGES" NUMBER NOT NULL,"CACHEHINT" NUMBER NO

  T NULL,"SCANHINT" NUMBER NOT NULL,"HWMINCR" NUMBER NOT NULL,"SPARE1" NUMBER,"SPA

  RE2" NUMBER) STORAGE ( OBJNO 14 TABNO 2) CLUSTER C_FILE#_BLOCK#(TS#,FILE#,BLOCK

  #)

  5

  CREATE TABLE CLU$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"TS#" NUMBER NOT NULL

  ,"FILE#" NUMBER NOT NULL,"BLOCK#" NUMBER NOT NULL,"COLS" NUMBER NOT NULL,"PCTFRE

  E$" NUMBER NOT NULL,"PCTUSED$" NUMBER NOT NULL,"INITRANS" NUMBER NOT NULL,"MAXTR

  ANS" NUMBER NOT NULL,"SIZE$" NUMBER,"HASHFUNC" VARCHAR2(30),"HASHKEYS" NUMBER,"F

  UNC" NUMBER,"EXTIND" NUMBER,"FLAGS" NUMBER,"DEGREE" NUMBER,"INSTANCES" NUMBER,"A

  VGCHN" NUMBER,"SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3" NUMBER,"SPARE4" NUMBER,"S

  PARE5" VARCHAR2(1000),"SPARE6" VARCHAR2(1000),"SPARE7" DATE) STORAGE ( OBJNO 5

  TABNO 2) CLUSTER C_OBJ#(OBJ#)

  6

  CREATE CLUSTER C_TS#("TS#" NUMBER) PCTFREE 10 PCTUSED 40 INITRANS 2 MAXTRANS 255

  STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREAS

  E 0 OBJNO 6 EXTENTS (FILE 1 BLOCK 57))

  7

  CREATE INDEX I_TS# ON CLUSTER C_TS# PCTFREE 10 INITRANS 2 MAXTRANS 255 STORAGE (

  INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO

  7 EXTENTS (FILE 1 BLOCK 65))

  18

  CREATE TABLE OBJ$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"OWNER#" NUMBER NOT N

  ULL,"NAME" VARCHAR2(30) NOT NULL,"NAMESPACE" NUMBER NOT NULL,"SUBNAME" VARCHAR2(

  30),"TYPE#" NUMBER NOT NULL,"CTIME" DATE NOT NULL,"MTIME" DATE NOT NULL,"STIME"

  DATE NOT NULL,"STATUS" NUMBER NOT NULL,"REMOTEOWNER" VARCHAR2(30),"LINKNAME" VAR

  CHAR2(128),"FLAGS" NUMBER,"OID$" RAW(16),"SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3

  " NUMBER,"SPARE4" VARCHAR2(1000),"SPARE5" VARCHAR2(1000),"SPARE6" DATE) PCTFREE

  10 PCTUSED 40 INITRANS 1 MAXTRANS 255 STORAGE ( INITIAL 16K NEXT 1024K MINEXTEN

  TS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 18 EXTENTS (FILE 1 BLOCK 121))

  36

  CREATE UNIQUE INDEX I_OBJ1 ON OBJ$(OBJ#) PCTFREE 10 INITRANS 2 MAXTRANS 255 STOR

  AGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 O

  BJNO 36 EXTENTS (FILE 1 BLOCK 217))

  10 rows selected.

  SQL>

  由这里我们可以看出,bootstrap$ 中实际上是记录了一些数据库系统基本对象的创建语句

  那对于我们数据库来说,也可以看做建立一个表结构,通过这个结构可以通过关系型数据库的方式去获取文件中数据

  ok,接下来我们看看trace文件中的内容,发现

  CREATE ROLLBACK SEGMENT SYSTEM STORAGE ( INITIAL 112K NEXT 1024K MINEXTENTS

  1 MAXEXTENTS 32765 OBJNO 0 EXTENTS (FILE 1 BLOCK 9))

  在数据库系统表空间的头部创建了系统回滚段(block 9 开始,1---8 属于数据文件头)

  再往下

  CREATE CLUSTER C_OBJ#("OBJ#" NUMBER) PCTFREE 5 PCTUSED 40 INITRANS 2 MAXTRANS

  255 STORAGE ( INITIAL 136K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645

  PCTINCREASE 0 OBJNO 2 EXTENTS (FILE 1 BLOCK 25)) SIZE 800

  这里同样是直接指定了该cluster 的段头位置 block 25

  SQL> select file_id,block_id from dba_extents where segment_name = 'C_OBJ#';

  1 25

  1 33

  1 41

  1 3241

  1 4441

  1 4473

  1 4489

  1 4513

  1 4529

  1 4561

  1 4585

  1 4609

  1 4641

  1 4681

  1 4753

  1 4833

  1 4873

  1 12681

  1 23689

  1 26249

  20 rows selected.

  CREATE INDEX I_OBJ# ON CLUSTER C_OBJ# PCTFREE 10 INITRANS 2 MAXTRANS 255

  STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645

  PCTINCREASE 0 OBJNO 3 EXTENTS (FILE 1 BLOCK 49))

  CREATE TABLE TAB$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"TS#" NUMBER NOT

  NULL,"FILE#" NUMBER NOT NULL,"BLOCK#" NUMBER NOT NULL,"BOBJ#" NUMBER,"TAB#"

  NUMBER,"COLS" NUMBER NOT NULL,"CLUCOLS" NUMBER,"PCTFREE$" NUMBER NOT NULL,

  "PCTUSED$" NUMBER NOT NULL,"INITRANS" NUMBER NOT NULL,"MAXTRANS" NUMBER NOT

  NULL,"FLAGS" NUMBER NOT NULL,"AUDIT$" VARCHAR2(38) NOT NULL,"ROWCNT" NUMBER,

  "BLKCNT" NUMBER,"EMPCNT" NUMBER,"AVGSPC" NUMBER,"CHNCNT" NUMBER,"AVGRLN"

  NUMBER,"AVGSPC_FLB" NUMBER,"FLBCNT" NUMBER,"ANALYZETIME" DATE,"SAMPLESIZE"

  NUMBER,"DEGREE" NUMBER,"INSTANCES" NUMBER,"INTCOLS" NUMBE

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