Capture From Oracle Using Direct Redo Access

In this capture method (Capture_Method=DIRECT), Data Source Solutions DSS reads transaction log records directly from the DBMS log file using the file I/O. This method is very fast in capturing changes from the Oracle database. The DIRECT log read method requires that the DSS Agent is installed on the source database machine.

Native Access to Redo Files

DSS's capture job needs permission to read Oracle's redo and archive files at the Operating System level. There are three different ways that this can be done;

1. Install DSS so it runs as Oracle's user (e.g. oracle).
2. Install DSS under a username (e.g. dss) which is a member of Oracle's default Operating System group (typically either oinstall or dba).
   • On Unix and Linux the default group of user oracle can be seen in the 4th field of its line in /etc/passwd. The DSS user be made a member of that group by adding its name to file /etc/group (e.g. line oinstall:x:101:oracle,dss).
   • On Windows, right-click My Computer and select Manage ▶ Local Users and Groups ▶ Groups ▶ ora_dba ▶ Add to Group ▶ Add.
     Note that adding DSS's user to group dba will also give DSS sysdba privilege.
3. Create special Access Control Lists (ACLs) on these files so that DSS's user can read them.

   • On Linux, the following commands can be run as user oracle to allow user dss to see redo files in $ORACLE_HOME/oradata/SID and archive files in $ORACLE_HOME/ora_arch. Note that an extra "default ACL" is needed for the archive directory, so that future archive files will also inherit the directory's permissions.

       $ setfacl -R -m u:dss:rx $ORACLE_HOME/oradata
       $ setfacl -R -m u:dss:rx,d:u:dss:rx $ORACLE_HOME/ora_arch
     

   • On Solaris, an extra command is needed to initialize the "default ACL":

       $ setfacl -m u:dss:rx $ORACLE_HOME/oradata
       $ setfacl -m u:dss:rx $ORACLE_HOME/oradata/SID
       $ setfacl -m u:dss:rx $ORACLE_HOME/oradata/SID/*
       $ setfacl -m d:u::rwx,d:g::rx,d:o:,d:m:rwx $ORACLE_HOME/ora_arch
       $ setfacl -m u:dss:rx,d:u:dss:rx $ORACLE_HOME/ora_arch
       $ setfacl -m u:dss:rx,d:u:dss:rx $ORACLE_HOME/ora_arch/*
       $ setfacl -m u:dss:rx $ORACLE_HOME/ora_arch/*/
     

Sometimes a Unix file system must be mounted in /etc/fstab with option acl otherwise ACLs are not allowed. On Linux, the user root can use command mount –o remount,acl to change this dynamically.