Reg hive files

The file name extensions of the files in these directories, or in some cases a lack of an extension, indicate the type of data they contain. The following table lists these extensions along with a description of the data in the file. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info.

Contents Exit focus mode. Then this stack is used to produce cumulative information about the layered key. For example, if you query the last written timestamp for a layered key, the most recent timestamp will be returned from the key node stack; if you enumerate key values for a layered key, key values from key nodes in the stack will be returned except tombstone values; if there are two or more values with the same name in the key node stack, a value from a lower "child" key node is used and returned.

When the Inherit class field is set to 0, the layered key will have the same class name as the key node originally accessed by a kernel. Otherwise, the layered key will receive the same class name possibly an empty class name as an upper "parent" key node from the stack having the Inherit class field set to 0.

Here, a "parent" key node doesn't mean a key node which offset is stored in the Parent field of a given key node. And a "child" key node doesn't mean a subkey of a given key node unless otherwise mentioned.

Instead, these relationships are created between key nodes in different registry hives a host registry hive, which represents the top layer, and a differencing registry hive, which represents the lower layer; both registry hives are used to provide the merged view of registry data, the top layer provides base data and the lower layer provides modifications to be applied on top of base data.

When the most significant bit is 1, data 4 bytes or less is stored in the Data offset field directly when data contains less than 4 bytes, it is being stored as is in the beginning of the Data offset field. The most significant bit when set to 1 should be ignored when calculating the data size. When the most significant bit is 0, data is stored in the Cell data field of another cell pointed by the Data offset field or in the Cell data fields of multiple cells referenced in the Big data structure stored in a cell pointed by the Data offset field.

The Big data is used to reference data larger than bytes when the Minor version field of the base block is greater than 3 , it has the following structure:. A data segment is stored in the Cell data field of a cell pointed by the Data segment offset field. A data segment has the maximum size of bytes. Data segments of a Big data record, except the last one, always have the maximum size.

If a cell to be marked as unallocated has an adjacent unallocated cell, these cells are coalesced, this is why a single unallocated cell may contain multiple remnant records entities. In Windows , the following record is written to the beginning of the Cell data field of an unallocated cell:. A transaction log file old format consists of a base block, a dirty vector, and dirty pages.

A backup copy of a base block isn't an exact copy anyway, the following modifications are performed on it by a hive writer:. The Dirty vector is stored starting from the beginning of the second sector of a transaction log file, it has the following structure:. Each bit of a bitmap corresponds to the state of a specific byte page within hive bins data to be written to a primary file from memory, regardless of a logical sector size of an underlying disk these pages don't overlap, there are no gaps between them :.

Bits of a bitmap are checked using the bt instruction or its equivalent based on bit shifting. This means that bits are packed into bytes, the first byte of a bitmap contains bits 1- 8, the second byte contains bits 9- 16, and so on. Within a byte, bit numbering starts at the least significant bit. Dirty pages are stored starting from the beginning of the sector following the last sector of a dirty vector.

Each dirty page is stored at an offset divisible by bytes and has a length of bytes, there are no gaps between dirty pages. The first dirty page corresponds to the first bit set to 1 in the bitmap of a dirty vector, the second dirty page corresponds to the second bit set to 1 in the bitmap of a dirty vector, etc. During recovery, contiguous dirty pages belonging to the same hive bin in a primary file are processed together, and a dirty hive bin is verified for correctness its Signature must be correct, its Size must not be less than bytes, its Offset must match the Offset of a corresponding hive bin in a primary file ; recovery stops if a dirty hive bin is invalid, an invalid dirty hive bin is ignored.

A transaction log file new format consists of a base block and log entries. This format was introduced in Windows 8. A modified partial backup copy of a base block is stored in the first sector of a transaction log file in the same way as in the old format and for the same purpose. However, the File type field is set to 6. Log entries are stored starting from the beginning of the second sector. Each log entry is stored at an offset divisible by bytes and has a variable size multiple of bytes , there are no gaps between log entries.

A dirty page reference describes a single page to be written to a primary file, and it has the following structure:. Dirty pages are attached to a log entry in the same order as in the Dirty pages references without an alignment or gaps. A hive is considered to be dirty i. If a hive isn't dirty, but a transaction log file new format contains subsequent log entries, they are ignored. LOG may be present as an artifact from an installation image.

LOG2 may be present as well. LOG1 file is used. LOG2 is performed this file will contain a cumulative log of dirty data, i. LOG1 and vice versa , keeping a cumulative log of dirty data. This allows a hive writer to keep a consistent copy of previous dirty data in another transaction log file on each write attempt if a system crash occurs when writing to a current transaction log file, thus leaving it in the inconsistent state, a primary file may be recovered later using a previous transaction log file.

After a successful write operation on a primary file, the first transaction log file will be used again. If an error occurs when writing a base block to a primary file in the beginning of a write operation in order to update the Primary sequence number and Last written timestamp fields , the whole operation fails without changing the log file being used. In the general case, the first transaction log file is used by a kernel to recover a dirty hive.

Before Windows 8, if a primary file contains an invalid base block i. Such a recovery algorithm is extremely ineffective, because it doesn't use the second transaction log file unless a base block of a primary file is invalid, and this base block is likely to be valid, because an error when writing a base block to a primary file in the beginning of a write operation will not trigger the switch to the second transaction log file, so the most probable event triggering this switch is a write error when storing dirty data in a primary file, that is likely to leave a valid base block in a primary file the mid-update state.

In Windows 8, the second transaction log file is used by a kernel to recover a dirty hive when the conditions mentioned above are met, with the following exceptions: the second transaction log file is used even if a base block of a primary file is valid, the second transaction log file is used even if its backup copy of a base block has a matching Last written timestamp.

The new algorithm is much more sound. In March , Microsoft released an updated kernel for Windows 7 6. When a dirty hive is loaded by a boot loader not by a kernel , the applicable transaction log file i. The first transaction log file is tried first. Another shortcoming in the implementation of the dual-logging scheme is that sequence numbers in a backup copy of a base block in a transaction log file are not used to record its mid-update state see above.

If a system crash occurs when writing to a transaction log file, there will be no clear indicators of which transaction log file is inconsistent. It is possible for an operating system to pick an inconsistent transaction log file for the recovery.

LOG2 and vice versa. This may divide log entries between two transaction log files; the first transaction log file isn't guaranteed to contain earlier log entries. If a primary file contains a valid base block, both transaction log files are used to recover the dirty hive, i. If a primary file contains an invalid base block, only the transaction log file with latest log entries is used in the recovery.

Flushing a hive ensures that its dirty data was written to a disk. When the old format of transaction log files is used, this means that dirty data was stored in a primary file. When the new format of transaction log files is used, a flush operation on a hive will succeed after dirty data was stored in a transaction log file but not yet in a primary file ; a hive writer may delay writing to a primary file up to an hour , in this situation dirty data becomes unreconciled.

As of Windows 8, the Clustering factor field is always set to 1, the logical sector size is always assumed to be bytes when working with related offsets and sizes. For example, a backup copy of a base block in a transaction log file is bytes in length regardless of a logical sector size of an underlying disk.

According to Microsoft, there is no support for a logical sector size different from bytes and bytes in Windows; a logical sector size equal to bytes is supported as of Windows 8 and Windows Server [ 2 ].

This is why the Clustering factor field is expected to be equal to 1. The Registry is a huge database that stores everything about your PC. The registry contains registry values which are instructions , located within registry keys folders that contain more data , all within one of several registry hives folders that categorize all the data in the registry using subfolders. It contains user-specific configuration information for all currently active users on the computer.

Then, navigate to the problem key and delete it like you would with any regular file. The Registry is a system file that holds lots of vital information about your PC and how it works. Over time, installing programs, updating software and attaching new peripherals can all add to the Registry. After reading the above content, it is very obvious to see that CCleaner is not the most ideal tool to clean your PC files. Registry fragments are a bit like duplicate keys.

These errors can occur when you uninstall or upgrade a piece of particular software, or even update it. System Shutdown Errors. Every time you turn off your computer, the system memory will save a copy of your registry. There are system-wide registry settings that apply to all users, and each Windows user account also has its own user-specific settings.

The registry hive that can give you information about most recently used items is the IP address for the default gateway that this system is using. Types of Registries. There are two major types of cancer registries : hospital-based registries and population-based registries. There are two sub-categories under hospital-based registries : single hospital registry and collective registry. However, you probably may not know that Windows 10, similar to previous versions, includes reg.

For help with the Reg. Solution Open the Registry Editor regedit. In the left pane, browse to the key you want to search. Enter the string you want to search with and select whether you want to search keys, values, or data. Click the Find Next button.