soft parse and hard parse! (from jl)
When you submit an SQL statement for processing, it passes through a number of stages before your server process finally gets to execute it and give you back the results. First your command is checked for syntax errors - basically, is the command correctly formed ? If the syntax check is passed, it is checked for semantic errors - things like do all the objects required exist, does the user have appropriate privileges etc. The next stage is to pass the command thorough a hashin
Cache Header and Tail (转载 ixora)
All datafile blocks are written and read by the cache layer of the Oracle kernel (KCB) generally through the database buffer cache. The cache layer reads and maintains a 20-byte header and 4-byte tail on each data block, called the cache header and tail. The cache header is called the common block header in V$TYPE_SIZE and elsewhere. Controlfile blocks also have a cache header and tail, although not all the fields are used. This is what the cache header and tail look like in a data
bbed 安装
cd $ORACLE_HOME/rdbms/lib ls -al *bb*.o -rw——- 1 oracle dba 3152 Nov 7 2006 sbbdpt.o -rw——- 1 oracle dba 2424 Nov 7 2006 ssbbded.o make -f ins_rdbms.mk $ORACLE_HOME/rdbms/lib/bbed [oracle@rhel4u5 lib]$ ls -l *bb* -rwxr-xr-x 1 oracle oinstall 554330 12月 23 23:09 bbed -rw-r--r-- 1 oracle oinstall 3124 2008-02-16 sbbdpt.o -rw-r--r-- 1 oracle oinstall 2802 2008-02-16 ssbbded.o cp $ORACLE_HOME/rdbms/lib/bbed $ORACLE_HOME/bin bbed Password: <