Oracle issues, 10 questions per day (eight)

oracle| problem
71. Application of kernel parameters? Shmmax meaning: This setting does not determine how much physical memory the Oracle database or operating system uses, but only determines the maximum amount of memory that can be used. 　　　　This setting also does not affect the kernel resources of the operating system. 　　　　Set method: 0.5* Physical Memory Example: set shmsys:shminfo_shmmax=10485760 shmmin meaning: The minimum size of shared memory. 　　　　Set method: Generally set to be 1. 　　　　Example: Set shmsys:shminfo_shmmin=1:shmmni meaning: The maximum number of shared memory segments in the system. 　　　　Example: Set shmsys:shminfo_shmmni=100 shmseg Meaning: The maximum number of shared memory segments that can be used by each user process. 　　　　Example: Set shmsys:shminfo_shmseg=20:semmni meaning: The maximum number of semaphore identifierer in the system. 　　　　Set method: The value of this variable is set to the Init.ora of all Oracle instances on this system and the value of that processes plus 10. 　　　　Example: Set semsys:seminfo_semmni=100 semmns Meaning: The maximum number of emaphores in the system. 　　　　Set method: This value can be computed in the following way: the sum of the values of the processes inside the Initsid.ora of each Oracle instance (minus the maximum processes parameter) + The number of the largest processesx2+10xoracle instance. 　　　　Example: Set semsys:seminfo_semmns=200 SEMMSL: Meaning: The maximum number of semaphore in a set. 　　　　Set up method: Sets the value of the largest processes in the Initsid.ora of all Oracle instances 10+. Example: Set semsys:seminfo_semmsl=-200

72. How to see which users have Sysdba, sysoper permissions?　　Sql>conn sys/change_on_install Sql>select * from V_$pwfile_users;　　73. How do I back up one or more tables separately? Exp User/Password tables= (table 1,..., table 2) 74.　　How do I back up one or more users separately? Exp System/manager owner= (user 1, user 2,..., user n) file= export file 75.　　How do I retrieve Full-text for a CLOB field?　　SELECT * from A WHERE dbms_lob.instr (a.a, ' K ', 1,1) >0;　　76. How do I display the current connection user? Show USER 77.　　How do I see the path where the data file is placed? Col file_name format A50 sql> Select Tablespace_name,file_id,bytes/1024/1024,file_name from Dba_data_files order by fi　　le_id;　　78. How do I view existing rollback segments and their status? Sql> Col segment Format A30 sql> SELECT segment_name,owner,tablespace_name,segment_id,file_id,status from Dba_ Rollback_segs

79. How do I change the check scope of a field's initial definition? sql> ALTER TABLE XXX drop constraint constraint_name; then create a new constraint: sql> ALTER TABLE XXX add constraint constraint_name　　Check ();　　What are the common system files for Oracle? These file information is displayed through the following view: V$database,v$datafile,v$logfile v$controlfile v$parameter;