ReservationCollection ReservationCollection ReservationCollection ReservationCollection Class

Definition

Manages the collection of space reservations made in a record sequence.

public ref class ReservationCollection abstract : System::Collections::Generic::ICollection<long>, System::Collections::Generic::IEnumerable<long>
public abstract class ReservationCollection : System.Collections.Generic.ICollection<long>, System.Collections.Generic.IEnumerable<long>
type ReservationCollection = class
    interface ICollection<int64>
    interface seq<int64>
    interface IEnumerable
Public MustInherit Class ReservationCollection
Implements ICollection(Of Long), IEnumerable(Of Long)
Inheritance
ReservationCollectionReservationCollectionReservationCollectionReservationCollection
Implements

Examples

Reservations can be performed in two ways as shown in the following examples. You can adopt the practices in the samples for robust processing. Notice that this task can only be performed when using the CLFS-based LogRecordSequence class.

//Using the ReserveAndAppend Method  
ReservationCollection reservations = recordSequence.CreateReservationCollection();  
long[] lengthOfUndoRecords = new long[] { 1000 };  
recordSequence.ReserveAndAppend(recordData,  
                                                     userSqn,  
                                                     previousSqn,  
                                                     RecordSequenceAppendOptions.None,  
                                                     reservations,  
                                                     lengthOfUndoRecords);  
recordSequence.Append(undoRecordData,    // If necessary …  
                                    userSqn,  
                                    previousSqn,  
                                    RecordSequenceAppendOptions.ForceFlush,  
                                    reservations);  
  
// Using the Manual Approach  
ReservationCollection reservations = recordSequence.CreateReservationCollection();  
reservations.Add(lengthOfUndoRecord);  
try  
{  
   recordSequence.Append(recordData, userSqn, previousSqn, RecordAppendOptions.None);  
}  
catch (Exception)  
{  
   reservations.Remove(lengthOfUndoRecord);  
   throw;  
}  
  
recordSequence.Append(undoRecordData, userSqn, previousSqn, RecordAppendOptions.ForceFlush, reservations);  

Remarks

This class represents a set of reservation areas that are made in a record sequence. Adding items to the collection allocates new reservations. Removing items from the collection frees those reservations.

An application reserves space in the log when it has data that is to be written to the log in the future, but cannot write it immediately. Reservations provide a guarantee that the data can be written to the log when the data is available to be written. When using logs, applications often reserve one or more log records in a marshaling area. You must reserve records prior to appending them.

Reservations can be used to guarantee that an operation can be completed before the data is committed; otherwise, the changes are rolled back. It can also be used to record an "undo action" in the log. During a rollback operation, a transactional resource manager (RM) must be able to recover its state if the RM is interrupted during the rollback operation. By using a reservation area, an RM can reserve space in a log before it is used.

The ReserveAndAppend method can either reserve space or append data, or both, depending on the parameters that are specified when making the call. As work progresses in a transaction, an application can append the undo information and reserve space for compensation records. During a rollback operation, compensation records that are created indicate what has been undone on the disk. The records are appended using space that has been previously reserved. This guarantees that an RM does not run out of log space, which is a fatal condition, while performing a rollback operation. If a log fills up during a transaction, an application can safely roll back a transaction without corrupting durable data.

CLFS is an ARIES-compliant logging system, meant for write-ahead logging. In write-ahead logging, an application writes an undo record before it performs the operation, reserving the amount of space it takes in the log to write a compensating record, which may be used during rollback. Later, the reserved space is used when the compensation record is actually written.

Applications can either reserve or access long space at any given time (they are mutually exclusive operations). After a commit record is written to the log, an application can free up the reservations for the compensation records. This action can be done by calling either the FreeReservation or ReserveAndAppend method. Calling the ReserveAndAppend method guarantees that the operation is atomic, while calling the FreeReservation method does not.

When you free records, you must free the same records that you reserved together in a previous call to the ReserveAndAppend method.

Note

Your implementation of IRecordSequence must implement the MakeReservation and FreeReservation methods to perform the actual reservation allocation and deallocation. In addition, your implementation must also call ReservationFreed when a record is written into a reserved space.

Constructors

ReservationCollection() ReservationCollection() ReservationCollection() ReservationCollection()

Initializes a new instance of the ReservationCollection class.

Properties

Count Count Count Count

Gets the number of reservations in the collection.

IsReadOnly IsReadOnly IsReadOnly IsReadOnly

Gets a value that indicates whether the collection is read-only.

Methods

Add(Int64) Add(Int64) Add(Int64) Add(Int64)

Allocates a reservation and adds it to the collection. This method cannot be inherited.

Clear() Clear() Clear() Clear()

Releases all of the reservations in the collection. This method cannot be inherited.

Contains(Int64) Contains(Int64) Contains(Int64) Contains(Int64)

Determines whether a reservation of the specified size has been made. This method cannot be inherited.

CopyTo(Int64[], Int32) CopyTo(Int64[], Int32) CopyTo(Int64[], Int32) CopyTo(Int64[], Int32)

Copies the entire collection to a one-dimensional array, starting at the specified index of the target array. This method cannot be inherited.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determines whether the specified object is equal to the current object.

(Inherited from Object)
Finalize() Finalize() Finalize() Finalize()

Allows the ReservationCollection to free resources before it is destroyed by the garbage collector.

FreeReservation(Int64) FreeReservation(Int64) FreeReservation(Int64) FreeReservation(Int64)

When overridden in a derived class, releases a reservation of the specified size.

GetBestMatchingReservation(Int64) GetBestMatchingReservation(Int64) GetBestMatchingReservation(Int64) GetBestMatchingReservation(Int64)

When overridden in a derived class, gets the best matching reservation for a given size.

GetEnumerator() GetEnumerator() GetEnumerator() GetEnumerator()

Returns an enumerator that can iterate through the ReservationCollection. This method cannot be inherited.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Gets the Type of the current instance.

(Inherited from Object)
MakeReservation(Int64) MakeReservation(Int64) MakeReservation(Int64) MakeReservation(Int64)

When overridden in a derived class, allocates a reservation of the specified size.

MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Creates a shallow copy of the current Object.

(Inherited from Object)
Remove(Int64) Remove(Int64) Remove(Int64) Remove(Int64)

Releases a reservation of the specified size, if one has been made. This method cannot be inherited.

ReservationFreed(Int64) ReservationFreed(Int64) ReservationFreed(Int64) ReservationFreed(Int64)

When overridden in a derived class, indicates that a reservation has been released.

ReservationMade(Int64) ReservationMade(Int64) ReservationMade(Int64) ReservationMade(Int64)

When overridden in a derived class, indicates that a reservation has been made.

ToString() ToString() ToString() ToString()

Returns a string that represents the current object.

(Inherited from Object)

Explicit Interface Implementations

IEnumerable.GetEnumerator() IEnumerable.GetEnumerator() IEnumerable.GetEnumerator() IEnumerable.GetEnumerator()

Returns an enumerator that can iterate through the ReservationCollection. This method cannot be inherited.

Extension Methods

CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>) CopyToDataTable<T>(IEnumerable<T>)

Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler) CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)

Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.

Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable) Cast<TResult>(IEnumerable)

Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable) OfType<TResult>(IEnumerable)

Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable) AsParallel(IEnumerable)

Enables parallelization of a query.

AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable) AsQueryable(IEnumerable)

Converts an IEnumerable to an IQueryable.

Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>) Ancestors<T>(IEnumerable<T>)

Returns a collection of elements that contains the ancestors of every node in the source collection.

Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName) Ancestors<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.

DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>) DescendantNodes<T>(IEnumerable<T>)

Returns a collection of the descendant nodes of every document and element in the source collection.

Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>) Descendants<T>(IEnumerable<T>)

Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName) Descendants<T>(IEnumerable<T>, XName)

Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>) Elements<T>(IEnumerable<T>)

Returns a collection of the child elements of every element and document in the source collection.

Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName) Elements<T>(IEnumerable<T>, XName)

Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.

InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>) InDocumentOrder<T>(IEnumerable<T>)

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.

Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>) Nodes<T>(IEnumerable<T>)

Returns a collection of the child nodes of every document and element in the source collection.

Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>) Remove<T>(IEnumerable<T>)

Removes every node in the source collection from its parent node.

Applies to