.NET/Java PDF, Tiff, Barcode SDK Library

The .NET-specific extensions to the PE format have surprising similarities to databases. Like a normal database, assemblies contain tables. These tables are called metadata tables. Metadata tables exist for type definitions, method definitions, and many other abstractions. Like database tables, each metadata table has a column structure specific for the abstraction. The structures for all tables start with a 32-bit column called a metadata token. Such a metadata token can be compared to a primary key in a database table. To establish relationships between the different abstractions stored in metadata tables, an approach similar to using foreign keys in databases is used: the structure of various metadata tables contains columns that store metadata tokens of other tables. As an example, since there is a one-to-n relationship between type definitions and methods (a type can have an arbitrary number of methods), there is a column for the parent type in the metadata table for methods. The Managed Reflection API also contains classes for all kinds of abstractions that can be stored in the metadata of assemblies. These abstractions include type definitions, methods (global functions as well as member functions of a managed type), and fields (member variables). All these types are semantically bound together via has-a relationships. An assembly has type definitions, type definitions have fields and methods, methods have parameters, and

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If you need to rename your redo log file, follow these steps: 1. Shut down the database and start it up in the mount mode: SQL> STARTUP MOUNT 2. Move the files to the new location with an operating system command: SQL> host! mv /u10/app/oracle/oradata/nina/log01.rdo /a10/app/oracle/oradata/nina/log01.rdo 3. Use the ALTER DATABASE RENAME datafile TO command to rename the file within the control file: SQL> ALTER DATABASE RENAME '/u10/app/oracle/oradata/nina/log01.rdo' TO '/a10/app/oracle/oradata/nina/log01.rdo';

You can drop an entire redo log group by using the following command: SQL> ALTER DATABASE DROP LOGFILE GROUP 3; To drop a single member of an online redo log group, use this command: SQL> ALTER DATABASE DROP LOGFILE MEMBER '/u01/app/oracle/oradata/nina/log01.rdo'; If the redo log file you want to drop is active, Oracle won t let you drop it. You need to use the following command to switch the log file first, after which you can drop it: SQL> ALTER SYSTEM SWITCH LOGFILE;

You can set the DB_BLOCK_CHECKSUM initialization parameter on to make sure Oracle checks for corruption in the redo logs before they re archived. If the online redo logs are corrupted, the file can t be archived, and one solution is to just drop and re-create them. But if there are only two log groups, you can t do this, as Oracle insists on having a minimum of two online redo log groups at all times. However, you can create a new (third) redo log group, and then drop the corrupted redo log group. Also, you can t drop an online redo log file if the log file is part of the current group. Your strategy then would be to reinitialize the log file by using the following statement: SQL> ALTER DATABASE CLEAR LOGFILE GROUP 1; If the log group has not been archived yet, you can use the following statement: SQL> ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 1;

You can use two key dynamic views, V$LOG and V$LOGFILE, to monitor the online redo logs. The V$LOGFILE view provides the full filename of the redo logs, their status, and type, as shown here:

#!/bin/sh CONFIG_FILE=$HOME/.whererc.$LOGNAME LOG_FILE=$HOME/.whererc.${LOGNAME}.log stty intr '^C' stty erase '^ '

SQL> SELECT * FROM V$LOGFILE; GROUP # STATUS TYPE --------------- -----3 STALE ONLINE 2 ONLINE 1 ONLINE 3 rows selected.

MEMBER -------------------------------------/u10/app/oracle/oradata/nina/log01.rdo /u10/app/oracle/oradata/nina/log01.rdo /u10/app/oracle/oradata/nina/log01.rdo

so on. To navigate from one type to another one, each of these types offers functions with the prefix Get. The following code uses Assembly::GetTypes to iterate through all type definitions of an assembly: // dumpAssemblyTypes.cpp // build with "CL /clr:safe dumpAssemblyTypes.cpp" using namespace System; using namespace System::Reflection; int main( array<String^>^ args) { for each (String^ url in args) { Assembly^ a = Assembly::LoadFrom(url); Console::WriteLine(a->Location); for each (Type^ t in a->GetTypes()) { Console::WriteLine(t); Console::WriteLine("Base class: {0}", t->BaseType); if (t->IsValueType) Console::WriteLine("This is a value type"); } } } Assembly::GetTypes returns an array of System::Type handles. Instances of System::Type are called type objects. Each handle refers to a type object that describes a public type of the assembly. System::Type allows you to find out almost everything about a type, including its name, base class, and supported interfaces. When a handle to a type object is passed to Console::WriteLine, then Type s overload for ToString is called. Type::ToString simply returns the namespace-qualified type name. However, the string returned is not a C++-like type name, but a language-neutral type name. Since most .NET languages use the dot character (.) as a namespace separator, Type::ToString does the same. There are various ways to get a type information object. As mentioned before, System::Object has a function called GetType(). Using this method, you can easily find out the type of any managed object and of any managed value. If the requested type is known at build time, the keyword typeid can be used. The following code checks if an object passed is of type String: bool IsString(Object^ o) { return o != nullptr && o->GetType() == String::typeid; }