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關于數據庫OPEN的深入探究

2024-07-21 02:38:02
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  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>
  
  首先我們來參考跟蹤文件的前部分(參考附件)
  這是第一個對象的創建
  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))
  
  接下來我們來看執行的是
  select line#, sql_text
  from
  bootstrap$ where obj# != :1
  (這里實際上是逐步提取內容建立字典表本身的結構,根據后面內容可知)
  
  那么在這里我們在數據庫中來看看 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 MAXEXTENTS 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 1024KMINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 8 EXTENTS (FILE 1 BLOCK73)) SIZE 225
  
  9
  CREATE INDEX I_FILE#_BLOCK# ON CLUSTER C_FILE#_BLOCK# PCTFREE 10 INITRANS 2 MAXTRANS 255 STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 9 EXTENTS (FILE 1 BLOCK 81))
  
  14
  CREATE TABLE SEG$("FILE#" NUMBER NOT NULL,"BLOCK#" NUMBER NOT NULL,"TYPE#" NUMBER NOT NULL,"TS#" NUMBER NOT NULL,"BLOCKS" NUMBER NOT NULL,"EXTENTS" NUMBER NOT NULL,"INIEXTS" NUMBER NOT NULL,"MINEXTS" NUMBER NOT NULL,"MAXEXTS" NUMBER NOT NULL,"EXTSIZE" NUMBER NOT NULL,"EXTPCT" NUMBER NOT NULL,"USER#" NUMBER NOT NULL,"LISTS" NUMBER,"GROUPS" NUMBER,"BITMAPRANGES" NUMBER NOT NULL,"CACHEHINT" NUMBER NOT NULL,"SCANHINT" NUMBER NOT NULL,"HWMINCR" NUMBER NOT NULL,"SPARE1" NUMBER,"SPARE2" NUMBER) STORAGE ( OBJNO 14 TABNO 2) CLUSTER C_FILE#_BLOCK#(TS#,FILE#,BLOCK#)
  
  5
  CREATE TABLE CLU$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"TS#" NUMBER NOT NULL,"FILE#" NUMBER NOT NULL,"BLOCK#" NUMBER NOT NULL,"COLS" NUMBER NOT NULL,"PCTFREE$" NUMBER NOT NULL,"PCTUSED$" NUMBER NOT NULL,"INITRANS" NUMBER NOT NULL,"MAXTRANS" NUMBER NOT NULL,"SIZE$" NUMBER,"HASHFUNC" VARCHAR2(30),"HASHKEYS" NUMBER,"FUNC" NUMBER,"EXTIND" NUMBER,"FLAGS" NUMBER,"DEGREE" NUMBER,"INSTANCES" NUMBER,"AVGCHN" NUMBER,"SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3" NUMBER,"SPARE4" NUMBER,"SPARE5" VARCHAR2(1000),"SPARE6" VARCHAR2(1000),"SPARE7" DATE) STORAGE ( OBJNO 5TABNO 2) CLUSTER C_OBJ#(OBJ#)
  
  6
  CREATE CLUSTER C_TS#("TS#" NUMBER) PCTFREE 10 PCTUSED 40 INITRANS 2 MAXTRANS 255STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 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 OBJNO7 EXTENTS (FILE 1 BLOCK 65))
  
  18
  CREATE TABLE OBJ$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"OWNER#" NUMBER NOT NULL,"NAME" VARCHAR2(30) NOT NULL,"NAMESPACE" NUMBER NOT NULL,"SUBNAME" VARCHAR2(30),"TYPE#" NUMBER NOT NULL,"CTIME" DATE NOT NULL,"MTIME" DATE NOT NULL,"STIME"DATE NOT NULL,"STATUS" NUMBER NOT NULL,"REMOTEOWNER" VARCHAR2(30),"LINKNAME" VARCHAR2(128),"FLAGS" NUMBER,"OID$" RAW(16),"SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3" NUMBER,"SPARE4" VARCHAR2(1000),"SPARE5" VARCHAR2(1000),"SPARE6" DATE) PCTFREE10 PCTUSED 40 INITRANS 1 MAXTRANS 255 STORAGE ( INITIAL 16K NEXT 1024K MINEXTENTS 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 STORAGE ( INITIAL 64K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 36 EXTENTS (FILE 1 BLOCK 217))
  
  10 rows selected.
  
  SQL>
  
  由這里我們可以看出,bootstrap$ 中實際上是記錄了一些數據庫系統基本對象的創建語句那對于我們數據庫來說,也可以看做建立一個表結構,通過這個結構可以通過關系型數據庫的方式去獲取文件中數據
  
  ok,接下來我們看看trace文件中的內容,發現
  
  CREATE ROLLBACK SEGMENT SYSTEM STORAGE ( INITIAL 112K NEXT 1024K MINEXTENTS
  1 MAXEXTENTS 32765 OBJNO 0 EXTENTS (FILE 1 BLOCK 9))
  
  在數據庫系統表空間的頭部創建了系統回滾段(block 9 開始,1---8 屬于數據文件頭)
  
  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
  這里同樣是直接指定了該cluster 的段頭位置 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" NUMBER NOT NULL,
  "KERNELCOLS" NUMBER NOT NULL,"PROPERTY" NUMBER NOT NULL,"TRIGFLAG" NUMBER,
  "SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3" NUMBER,"SPARE4" VARCHAR2(1000),
  "SPARE5" VARCHAR2(1000),"SPARE6" DATE) STORAGE ( OBJNO 4 TABNO 1) CLUSTER
  C_OBJ#(OBJ#)
  
  我們可以看到,從tab$ 開始,存儲發生了變化,
  STORAGE ( OBJNO 4 TABNO 1) CLUSTER C_OBJ#(OBJ#)
  那這里的 objno 4 tabno 1 表示什么意思呢?
(通過 cluster C_OBJ#(OBJ#)我們就可以找到表tab$自身)
  
  SQL> select * from tab$ where obj# = 4 and tab# = 1;
  
  OBJ# DATAOBJ# TS# FILE# BLOCK# BOBJ# TAB#
  ---------- ---------- ---------- ---------- ---------- ---------- ----------
  COLS CLUCOLS PCTFREE$ PCTUSED$ INITRANS MAXTRANS FLAGS
  ---------- ---------- ---------- ---------- ---------- ---------- ----------
  AUDIT$ ROWCNT BLKCNT EMPCNT
  -------------------------------------- ---------- ---------- ----------
  AVGSPC CHNCNT AVGRLN AVGSPC_FLB FLBCNT ANALYZETI SAMPLESIZE
  ---------- ---------- ---------- ---------- ---------- --------- ----------
  DEGREE INSTANCES INTCOLS KERNELCOLS PROPERTY TRIGFLAG S

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