Programming Distributed Applications with COM and Microsoft Visual Basic 6.0: Build N-Tier Business Objects for Distributed Solutions by Ted Pattison

Page numbers in italics refer to figures or tables.

A
Abort method, 210, 211, 215
abstract base classes, 45-46
access permissions, 272
ACID rules
    defined, 202
    in distributed transactions, 209
    usage overview, 203-6
Activate method, 190
activation, COM
    local vs. remote, 163
    out-of-process, 73-74, 78, 84
    overview, 56-58
    in server packages, 182-83
Active Server Pages (ASP)
    architecture of, 283-86
    built-in objects, 284, 289-91
    creating, 283-84
    creating Visual Basic objects from, 286-92
    defined, 283
    and IIS Application Designer, 17, 18, 292-93
    running applications, 285, 286
    running MTS transactions from, 286, 287
    transactional support, 288-89
ActiveX components, in MSMQ, 242, 246
ActiveX Data Objects (ADO), 207, 224, 286
ActiveX DLLs
    vs. ActiveX EXEs, 78, 79
    apartment-threaded, 147-48
    building, in Visual Basic, 81-85
    debugging, 196-99
    and global variables, 152
in MTS environment, 180, 182, 185-89, 195-96
    MTS transaction support, 212-13
    when to use, 78, 79
ActiveX EXEs
    vs. ActiveX DLLs, 78, 79
    building, in Visual Basic, 81-85
    and global variables, 152
    multithreaded, 148-50
    and secondary threads, 153, 154-55
    and thread pooling, 150
    when to use, 78-79
ActiveX vs. COM, 6
activities, MTS, 191-93
activity threading, 155-56
AddRef method, 62, 63, 64
administration queues, 266
apartments. See also threads
    creating, 145-46, 148, 149-50, 154
    and global variables, 151-52
    in MTS, 191-93
    multithreaded (MTA) model, 142-44
    overview, 141-42
    single-threaded (STA) model, 142-45
apartment-threaded model, 142. See also single-threaded apartment (STA) model
AppIDs
    configuring, 169-70, 173, 272
    in MTS, 183, 184, 273
applications. See also distributed applications; transactional applications
    monolithic development vs. COM, 3-4
    using interfaces in design, 38-39
    Web-based, 283-93
AppServer class, 186
architecture, two-tier vs. N-tier, 7-13, 177. See also three-tier architecture; two-tier architecture
array data type, 119-20
Arrived event, 252
ASP. See Active Server Pages (ASP)
ASP type library, 289-90, 290
asynchronous communication, and Microsoft Message Queue, 16-17, 235
asynchronous method calls, 155, 155
atomic transaction requirement, OLTP, 202, 203
authentication, 167
automation, 65-70, 93, 131

B
backup site controllers (BSCs), 239, 241
BeginTransaction method, ITransactionDispenser interface, 210, 215
BeginTransaction method, MSMQTransactionDispenser object, 261
bidirectional communication, 128-35
Binary Compatibility mode, 91, 92, 195, 196
binary reuse
    as basis for COM, 2, 4
    and C++, 43-44
    and DLLs, 2, 4
    and object-oriented programming, 43
    and Windows operating system, 43
binding
    early, 68-69
    late, 66-67, 68
    and RPC, 161
    types of, 68-69
    vTable, 69
black-box reuse, 28, 29
built-in ASP objects, 284, 289-91
business objects, 10-12, 11, 12
ByRef parameter, 118, 123-24
Byte arrays, 253-54
ByVal parameter, 118, 123, 124

C
C and C++ programming languages. See also Visual C++
    and abstract base classes, 45-46
    and binary reuse, 43-44
    and class factories, 59
    and COM, 5
    and custom marshaling, 73
    developing eventing service, 294-95
    and distributed transactions, 210-11
    and dynamic binding, 46-47
    friend methods, 97
    and GUIDs, 55
    vs. Interface Definition Language, 49-50
    and IUnknown interface, 63
    limitations for component-based development, 43-45
    memory allocation, 62
    and multithreading, 144, 145
    naming interfaces, 114-15
    and remote activation, 174
    and special data types, 123
    and threads, 139
vs. Visual Basic, 3, 54, 55
callback interfaces, 131-34, 174
calling context, 188-89
CanBePooled method, 191
Caption property, 246
CICS, 207
circular references, 64
class-based references, 20-21, 22
classes
    and implementation inheritance, 23
    implementing interfaces, 29-30
    installing in MTS server packages, 182
    vs. interfaces, 31
    persistable, 258-60
    and public interfaces, 21-22
    selecting type of COM server for, 77-80
    setting procedure attributes, 96-97
    superclasses vs. subclasses, 23
    and threads, 146
    Web classes, 292-93, 292
class factories, 58-59
class identifiers (CLSIDs), 55-56, 73, 84, 85, 90, 91, 146, 163, 165, 173, 174, 182, 183
class modules, 30, 31, 32-33, 94
Close method, 244
CLSIDs. See class identifiers (CLSIDs)
coclasses, defined, 47-48
CoCreateGUID function, 55
CoInitializeEx function, 147
collection objects, 124
COM. See Component Object Model (COM)
COM+
    eventing service, 295
    load balancing service, 297
    middleware features, 298
    queued components feature, 296-97
    role of MTS, 299-300
    threading in, 155-56
    and Windows NT Server, 14
COM activation. See activation, COM; remote activation
COM applications, defined, 169
COM DLLs, 77. See also ActiveX DLLs
COM exceptions, 101-4
COM EXEs, 77. See also ActiveX EXEs
COM library, 54, 55
Commit method, 210, 211
committed transactions, 203
COM objects
    activating, 56-58
    built-in ASP objects as, 290
    overview, 61
compatibility, component versions
    levels of, 87
    and MTS, 195
    project settings, 89-91
Component Object Model (COM). See also COM+
    vs. ActiveX, 6
    architectural requirements, 42
    and binary reuse, 2, 4
    vs. DCOM, 7
    declarative vs. programmatic security, 166, 272
    error-raising conventions, 104-5
    exception handling, 101-4
    history of, 41-43
    initial design requirements, 43-54
and interface-based programming, 5-6
    interface-based programming as basis, 38-39
    and Interface Definition Language (IDL), 49, 110-12
    interprocess capability, 3, 42, 115-23
    and language independence, 48
    mapping to Visual Basic, 51-53
    vs. monolithic application development, 3-4
    and MTS, 195
    vs. OLE, 6, 42-43
    and out-of-process communications, 4-5
    overview, 1-3
    relationship to object-oriented programming, 2-3, 42, 107
    and remote method calls, 4-5, 5, 6
    role of interfaces, 34
    and RPC, 160-64
    threading models, 142-45
    and Visual Basic, 3
    and Web-based applications, 283
COM security, 166, 272-74
COM servers
    ActiveX DLLs vs. ActiveX EXEs, 79
    component packaging, 77-80
    and component versioning, 86-93
    creating, 81-85, 93
    in-process vs. out-of-process, 77-79
    registering, 83-84
    and Windows Registry, 82-83
COM Specification, 47-48
concurrency, 140-41
connected networks (CNs), 239
connection pooling, 224-26
consistency transaction requirement, OLTP, 202, 203, 214
constants, enumerating, 95
container applications, 79, 80
Contents property, 256
context, calling, 188-89
context wrappers, 185, 185, 189, 216, 216, 217-18
coordinating transaction manager (CTM), 208-9, 208. See also Distributed Transaction Coordinator (DTC)
CorrelationID message property, 248
CreateInstance method, 193, 214, 220, 287
Create method, 243
CreateObject function, 85, 153, 173, 189, 193-94
CreatePropertyGroup method, 280-81
CreateProperty method, 281-82
CreateThread function, 146-47
custom callback interfaces, 131-34
custom marshaling, 73, 124-26
cyclic deadlocks, 228

D
DACL. See discretionary access control list (DACL)
database management systems (DBMSs)
    and distributed transactions, 211
    and lock management, 204-6
    making connections, 223-28
    and online transaction processing, 202, 206, 207
    and two-tier architecture, 8-9, 10, 177
data types, primitive, 119-23
DBMS. See database management systems (DBMSs)
DCOM. See Distributed COM (DCOM)
Dcomcnfg.exe file
    Applications tab, 169
    Default Properties tab, 167, 167-69
    defined, 165
    Identity tab, 171-72, 171
    Location tab, 173, 174
    Security tab, 170, 170
Deactivate method, 190
dead letter queues, 265-66
deadlocks, 228-30
debugging MTS components
    using MsgBox statement, 196, 197
    using Windows NT event log, 196, 197
    in Visual Basic, 196, 198-99
    in Visual C++, 196, 197
declarative security, 166, 272, 273-74
declarative transactions, 15, 212. See also MTS transactions
Delivery message property, 247-48
DisableCommit method, 217-18, 221, 222
discretionary access control list (DACL), 166
distributed applications
    client-side configuration, 173-74
    creating middleware for, 293-300
    designing, 271-300
    load balancing across servers, 17, 236-37, 236, 297-98
    queue listener application, 295-97, 296
    role of message queues, 234-38, 234
    and RPC, 162-64
    scalable notification system, 293-95
    server-side configuration, 165-72
    Web-based, 283-93
Distributed COM (DCOM). See also distributed applications
    configuring, 165, 167-72
    and firewalls, 175
    initial release pros and cons, 175
    overview, 7
    and RPC, 162-64
distributed computing. See also distributed applications; Distributed COM (DCOM)
    and Microsoft Message Queue, 16-17
    and Microsoft Transaction Server, 15, 16
    need for application scalability, 16-17
    and object-oriented programming, 3
    and Windows NT Server, 14-18
Distributed Computing Environment (DCE), and RPC, 160
Distributed Transaction Coordinator (DTC)
    enlisting connections, 223-224, 223
    and MTS, 212-32
    overview, 209, 210
    writing applications directly against, 210-11
distributed transactions
    ACID rules in, 209
    and DTC, 210-11
    and MTS, 212-32
    overview, 207-9
    steps in running, 208-9
    and transaction managers, 207, 208, 210-11
    and two-phase commit protocol, 207, 209, 223, 223
DllHost.exe container application, 79
DLLs. See ActiveX DLLs; dynamic-link libraries (DLLs)
domain controllers, 174
done flag, 216, 216
doomed flag, 216-17, 216
DTC Proxy Core Object, 210
DTC transactions, 215
dual interfaces, 67-68
durability transaction requirement, OLTP, 202, 203
dynamic binding, 26, 46-47
Dynamic Data Exchange (DDE), 42
dynamic-link libraries (DLLs), 2, 4, 78-79. See also ActiveX DLLs

E
EnableCommit method, 218
encapsulation
    and C++, 44-45
    and COM, 4
    and inheritance, 29-30
Encina, 209
enlisted objects, 226
enlisting connections, 223-224, 223
enumerations, 95-96
error handling, 101-5
events, MSMQ, 250-52
events, Visual Basic
    building scalable application, 293-95, 294
    using, 129-31
exporting packages, 183-84
extending interfaces, 37, 114-15
external transactions, MSMQ, 260, 263-64

F
facility codes, 99-101
factoring interfaces, 112-14
    factory pattern, 58
firewalls, using DCOM across, 175
flags, internal, 216, 216
FormatName property, 245-46
form-based applications, multithreading in, 153-55
free-threaded model, 142. See also multithreaded apartment (MTA) model
friend methods, 97

G
"garbage collection," 164
GetObjectContext method, 186, 186, 187, 189, 195
GetOriginalCallerName method, 278
global classes, 94-95
global data, sharing across MTS objects, 279-83
globally unique identifiers (GUIDs), 55-56, 90-91, 183
GlobalMultiUse classes, 94, 95
GlobalSingleUse classes, 94
global variables, and apartment threading, 151-52
GUIDs. See globally unique identifiers (GUIDs)

H
happy flag, 216, 216, 217-18
HRESULTs, 98-101
HTML files. See Active Server Pages (ASP)
HTML templates, 292

I
IDE. See Integrated Development Environment (IDE)
IDispatch interface
    vs. IUnknown interface, 111-12
    overview, 66-67
    and Visual Basic events, 131
    vs. vTable binding, 131
IDL. See Interface Definition Language (IDL)
ID message property, 248
IID forwarding, 88-89
IIDs. See interface identifiers (IIDs)
IIS. See Internet Information Server (IIS)
IIS Application Designer (IISAD), 17, 292-93
IIS In-Process Applications, 285
IMarshal interface, 124
impersonation, 168-69
implementation inheritance
    and code reuse, 23-25
    and COM, 4
    hierarchies, 24-25, 25
    Java example, 23-24
    overview, 23, 24
    and polymorphism, 25-26, 26
    problems with, 27-28
    and Visual Basic, 20
    when to use, 24, 27
    and white-box reuse, 27, 28
inheritance, interface, 29-30, 112-13
inheritance hierarchies, 24-25, 25. See also implementation inheritance
Initialize procedure, 189
InitProperties method, 258
in-process servers, 77, 78, 84
installing Microsoft Message Queue (MSMQ), 240-41
Instancing settings, 94
Integrated Development Environment (IDE), 53, 55, 78, 90, 91, 109-10
interactive users, 172
interface-based programming, 5-6, 19-20
Interface Definition Language (IDL)
    benefits of using, 50
    defining interfaces in, 110-12
    overview, 48-49
    and RPC, 160
    and Visual Basic, 49, 53-54, 110-12, 114-15
interface identifiers (IIDs), 55-56, 90, 91, 92, 182
interface inheritance, 29-30, 112-13
interfaces
    as basis for COM, 38-39
    benefits of using, 34-36
    vs. classes, 31
    and code reuse, 20
    and COM, 5-6, 19
    custom callback, 131-34
    as data type, 5-6, 28
    defined, 28
    defining in separate type libraries, 109-10
    defining properties in, 32
    design decisions, 108-15
    dual, 67-68
    extending, 37, 114-15
    factoring, 112-14
    and GUIDs, 55-56
    hidden, 51
    IUnknown vs. IDispatch, 111-12
    logical names for, 114-15
    multiple, 35-36, 64, 65
    outbound, 128-35
    and proxy/stub pairs, 71
    role in COM, 34
    RPC, 160-61
    separating from implementation, 28-37
    setting procedure attributes, 96-97
    user-defined, 20, 37, 38-39, 69-70, 108-15
    using, 33-39
    version-compatible, 87, 88-89
    version-identical, 87
    and Visual Basic, 20, 30-32, 51-54, 68, 69, 113-14
    writing in IDL, 53-54, 110-12
internal transactions, MSMQ, 260-63
Internet Information Server (IIS), 17, 18, 283, 284-85, 290
IPersistStorage interface, 258, 259
IPersistStream interface, 258, 259
IsCallerInRole method, 277-78
isolation levels, 205-6, 228
isolation transaction requirement, OLTP, 202, 204-6
ISupportErrorInfo interface, 101-2
ITransactionDispenser interface, 210, 215
ITransaction interface, 210, 211, 215
IUnknown interface
    AddRef method, 62, 63, 64
    vs. IDispatch interface, 111-12
    overview, 61-65
    QueryInterface method, 64-65
    Release method, 62, 63, 64

J
Java, 2, 23-24, 48
journal queues, 264-65

L
late binding, 66-67, 68
launch permissions, 272
legacy DLLs, 79-80
library packages, 180, 275, 278
lifetime management, 62-64
load balancing, 17, 236-37, 236, 297-98
location transparency, 5, 71, 74-75, 115
locking
    conflicts in, 228-30
    levels of granularity, 204
    overview, 204
    in property groups, 281
    read locks, 204-5, 229
    shared locks, 204-5
    update locks, 229-30
    write locks, 204-5, 228, 229
lock management, 204-6

M
marshaler, universal, 72, 82, 115, 116, 120-21, 123-24, 125
marshaling
    custom, 73, 124-26
    defined, 71, 72
    and remote interfaces, 115, 116, 117-18, 120-21, 121, 122, 123
    standard, 72
    using smart proxy objects, 126-28
    and Visual Basic, 72, 124-26
memory, 62, 279-83
message bodies
    defined, 246
    passing parameterized information, 252-60
    passing VBA strings, 246-52
    and persistent objects, 258-60
    and PropertyBag objects, 256-57
    role of Byte arrays, 252-54
    and string parsing, 254-56
message headers, 246
message queues. See queues
messages. See also message bodies; queues
    priority levels, 246-47
    properties of, 246-48
    queue listener application, 295-97, 296
    reading and removing, 248-50
    receiving, 248-49
    sending, 246-47
    transactional, 260-64
    viewing without removing, 250
methods
    changing implementations, 92
    and HRESULTs, 98-101
    implementing subset of, 112
    marking as friends, 97
    out-of-process calls, 72, 115, 116, 116
    return values, 98-101
    round-trip calls, 115-17
    setting attributes, 96-97
Microsoft Distributed Transaction Coordinator. See Distributed Transaction Coordinator (DTC)
Microsoft IDL compiler, 110, 161-62
Microsoft Message Queue (MSMQ)
    ActiveX components, 242
    creating private queues, 245-46
    creating public queues, 242-45
    and Distributed Transaction Coordinator (DTC), 209
    installing, 240-41
    internal vs. external transactions, 260-64
    MSMQ events, 250-52
    overview, 16-17, 238-40
    programming MSMQ objects, 242-60
    sending messages, 246-47
    transactional messages in, 260-64
Microsoft SQL Server. See SQL Server
Microsoft Transaction Server (MTS). See also MTS components
    in COM+, 299-300
    concurrency model, 191-94
    as container application, 178-79
    and declarative transactions, 212-32
    as development environment, 195-96
    and Distributed Transaction Coordinator (DTC), 209
    and distributed transactions, 207, 209, 210
    and DTC, 212-32
    mtx.exe container application, 80
    and N-tier architecture, 177-78
    overview, 15, 16, 177-78
    security model, 272-78
    and stateless programming, 230-32
    Windows NT requirements, 194-95
middle-tier. See middleware
middleware, 293-300
MIDL compiler, 110, 161-62
MQSeries, 233
MsgBox statement, 154, 196, 197
MSMQCoordinatedTransactionDispenser component, 263
MSMQ enterprises, 238-39
MSMQEvent object, 251-52
MSMQ events, 250-52
MSMQ Explorer, 240-41, 242, 247
MSMQ Information Store (MQIS), 239, 240, 241
MSMQMessage object, 246
MSMQQuery object, 243-44
MSMQQueueInfo object, 242, 243, 244
MSMQQueue object, 244, 248, 250, 251-52
MSMQ routing servers, 239
MSMQ sites, 239
MSMQTransactionDispenser object, 261
MSMQTransaction object, 261
MS-RPC, 161-62
MTS. See Microsoft Transaction Server (MTS)
MTS applications
    enlisting connections, 223-224, 223
    resource dispensers for, 224-25, 279-83
    secured, 274-76
    and stateless programming, 230-32
MTS components. See also MTS objects
    and activation, 182-83
    creating, in Visual Basic, 180-82, 189
    debugging, 196-99
    defined, 179
    server packages vs. library packages, 179-80
    transaction support settings, 212-13, 212, 213, 214
MTS Executive
    creating objects inside transactions, 213-15
    defined, 180
    overview, 184-85
MTS Explorer, 180, 181, 182, 183-84, 195, 196, 212
MTS objects. See also MTS transactions
    connection pooling, 224-26
    creating, 189, 190, 193-94, 213-15
    enlisted, 226
    life cycle of, 189-91
    propagating into existing activities, 192-93
    root, 214, 215, 216-17, 221-22, 225
    secondary, 220-22, 226
    sharing global data across, 279-83
MTS programmatic security, 272, 276-78
MTS resource dispensers, 224-25, 279-83
MTS roles, 273-76
MTS run time. See MTS Executive
MTS server packages. See server packages
MTS transactions
    ASP scripting objects in, 288-89
    business logic vs. data access code, 226-28
    completing vs. aborting, 216-18, 216
    connecting objects to resource manager, 223-224, 223
    creating objects inside, 212-14
    vs. DTC transactions, 215
    internal flags, 216, 216
    as logical transactions, 215
    multiobject, 220-22
    running from ASP pages, 286, 287-88
    secondary objects, 220-22
    sending and receiving messages in, 263-64
MTSTTransactionMode property, 212-13, 213
mtxas.dll file, 185
mtxex.dll file, 80, 180, 274
mtx.exe file, 80, 178-79, 274
mtxspm.dll file, 279
multiobject MTS transactions, 220-22
multiple interfaces, 35-36, 64, 65
multithreaded apartment (MTA) model, 142-44
multithreading. See also apartments
    and concurrency, 140-41
    and data synchronization, 140-41, 279
    in form-based applications, 153-55
    and global data sharing, 279-83
    and Visual Basic, 146-52
    when to use, 137-38, 156-57
MultiUse classes
    adding to ActiveX DLLs, 179, 180, 182
    and ObjectControl interface, 190
    overview, 94-95
    vs. user-defined interfaces, 108

N
Nelson, Mike, 175
New operator, 57, 84, 153, 189, 193-94
No Compatibility mode, 90
notification systems, scalable, 293-95
N-tier architecture. See also three-tier architecture
    and Microsoft Transaction Server, 177-78
    overview, 13, 13
    and RPC, 162-64

O
Object Browser, 186, 290, 290
ObjectContext interface, 187-89, 276-77, 278, 287
ObjectControl interface, 189-90
Object data type, 67
object-oriented programming (OOP)
    and binary reuse, 43
    and distributed computing, 3
    implementation inheritance feature, 23-28
    polymorphism feature, 25-26, 26
    relationship to COM, 2-3, 42, 107
and RPC, 161
object pooling, 190
objects. See also MTS objects; root objects
    activation overview, 56-58
    and bidirectional communication, 128-35
    calling context, 188-89
    circular references to, 64
    class factories, 58-59
    extending, 37, 86-87, 92, 114-15
    in-process vs. out-of-process, 115-23
    lifetime management, 62-63
    and outbound interfaces, 128-35
    persistent, 258-60
    public interfaces, 21, 22
    stateless, 230-32
ODBC Driver Manager, 223, 224-25
ODBC drivers, 211, 224
OLE32.DLL file, 54, 57
OLE automation, 65. See also automation
OLE Transactions protocol, 209, 223
OleView utility, 50, 50, 111
OLE vs. COM, 6, 42-43
OLTP. See online transaction processing (OLTP)
online transaction processing (OLTP)
    ACID rules, 202, 203-6
    concurrency vs. isolation, 228-30
    distributed transactions, 207-11
    overview, 202-7
    role of MTS, 15, 207
    simple transactions, 206-7
    transaction requirements, 202
    Web-based, 17, 18
Open method, 244
Open Software Foundation (OSF), 160
Oracle, 8, 202, 204, 211, 223
outbound interfaces, 128-35
out-of-process activation, 73-74, 78, 84
out-of-process method calls, 72, 115, 116, 116
out-of-process servers, 77, 78-79, 80, 83-84, 165

P
packages
    creating, 181-82
    exporting, 183-84
    server packages vs. library packages, 179-80
    viewing list in My Computer, 180-81
packaging components, 77-80
.pak files, 183
parsing strings, 254-56
participating transaction manager (PTM), 208, 208, 209. See also Distributed Transaction Coordinator (DTC)
PathName property, 242, 243, 245
PeekCurrent method, 250
peeking, defined, 234
Peek method, 250
PeekNext method, 250
persistable classes, 258-60
persistent objects, 258-60
ping algorithm, 164
plug-compatible objects, 26
polymorphism, 4, 6, 25-26, 26, 35
pooling ODBC connections, 224-26
primary enterprise controllers (PECs), 239, 240, 241
primary site controllers (PSCs), 239, 240, 241
primary thread, defined, 139
primitive data types, 119-23
private queues, 245-46
Procedure Attributes dialog box, 96-97
Procedure IDs, 97
processes, defined, 138
ProgIDs, 85
programmatic security, 166, 272, 276-78
programming, interface-based, 5-6. See also object-oriented programming (OOP)
programming languages. See also C and C++ programming languages; Visual Basic
    and COM, 2, 48
    and implementation inheritance, 23-24, 27
    and polymorphism, 25-26
Project Compatibility mode, 90
Project Properties dialog box, 89-91
properties
    in property groups, 279, 281-82
    setting attributes, 96-97
    shared, 279, 281-82
PropertyBag objects, 256-57, 258
property groups, 279, 280-81
protected properties, 27
proxy objects, 70-71, 71, 72, 126-28
proxy/stub pairs
    and out-of-process objects, 115
    overview, 70-71
    and Registry, 82
    responsibilities of, 72
public interfaces, 21, 22
PublicNotCreatable class module, 52-53
public queues, 242-45

Q
QueryInterface method, 64-65
queued components, 296-97
queues. See also Microsoft Message Queue (MSMQ)
    administration, 266
    creating, 242-45
    dead letter, 265-66
    journal, 264-65
    listener application, 295-97, 296
    overview, 234-38
    private, 245-46
    public, 242-45
    response, 266-69
    vs. RPC, 235-38
    transactional, 237-38, 237, 260-64
    types of, 264-69

R
Read Committed isolation level, 205, 206
reader applications, 234
read locks, 204-5, 229
ReadProperties method, 258, 259
ReadProperty method, 257
Read Uncommitted isolation level, 205, 206
ReceiveCurrent method, 250
Receive method, 248, 249, 250
receiver applications, 234, 234
refreshing Registry, 196
registering COM servers, 83-84
Registry. See also AppIDs
    and COM servers, 82-83
    and GUIDs, 55
    refreshing, 196
Release method, 62, 63, 64
remote activation
    and client-side configuration, 173-74
    vs. local activation, 163
    overview, 163-64
    and Service Control Manager (SCM), 163-64
remote method calls, 4-5, 5, 6, 72
remote objects, binding, 73-74
Remote Procedure Call (RPC)
    background, 160-62
    and COM, 160-64
    and HRESULTS, 98-101
    importance of, 162, 163
    limitations of, 161, 235-37
    vs. message queues, 235-38
    MS-RPC, 161-62
    and object-oriented programming, 161
    standard, 7, 160, 161-62
Remote Server Name property, 184
Repeatable Read isolation level, 205, 206
resource dispensers
    ODBC Driver Manager as, 224-25
    Shared Property Manager as, 279-83
resource managers (RMs), 207, 208, 208, 211, 223-224, 223
response queues, 266-69
roles, MTS, 273-76
root objects. See also secondary objects
    and connection pooling, 225
    defined, 214
    how they work, 215
    in multiobject transactions, 220-22
    role in MTS transactions, 216-17
round-trip method calls, 115-17
routing servers, 239
RPC. See Remote Procedure Call (RPC)
run-time environment, 80

S
SafeRef method, 186, 186, 187
scalability, application, 16-17
scalable eventing architecture, 293-95, 294
SCM. See Service Control Manager (SCM)
ScriptingContext interface, 289, 290-91
secondary objects, 220-22, 225, 226
secondary threads, 153, 154-55, 154
secured MTS applications, 274-76
security
    authentication levels, 167-69
    configuring DCOM, 167-69
    declarative vs. programmatic, 166, 272
    impersonation levels, 168-69
    MTS model, 272-78
    programmatic, 166, 272, 276-78
Security property, 278
sender applications, 234, 234
Send method, 246, 249
Serializable isolation level, 206, 228
Server object, 286
server packages
    activation in, 182-83
    creating, 181-82
    vs. library packages, 180
    MTS roles in, 274-76
    overview, 179-80
    and security checking, 276
    testing, 195-96
servers. See also COM servers
    load balancing across, 17, 236-37, 236, 297-98
    for MSMQ, 239-40
Service Control Manager (SCM)
    and class factories, 58-59
    and MTS objects, 182
    and object activation, 57-58, 73-74, 78, 84, 85
    overview of COM activation, 57-58
    and remote activation, 163-64
SetAbort method, 218-19, 220, 221, 222
SetComplete method, 218-19, 220, 221, 222
shared locks, 204-5
shared properties
    in COM+, 283
    creating, 281-82
    creating groups, 280-81
    reading and writing to, 282
    setting default value, 282
Shared Property Manager (SPM), 279-83
sharing MTS objects, 279-83
single-threaded apartment (STA) model, 142-45, 279
SingleUse classes, 94
smart proxy objects, 126-28
software. See applications
source journaling, 264-65
SPM. See Shared Property Manager (SPM)
SQL Server
    and deadlocks, 229-30
    and MSMQ enterprises, 239
    and transaction processing, 202, 204, 206, 209, 211, 223, 224
    and two-tier architecture, 8, 9
SQLSetConnectAttr function, 211
standard marshaling, 72. See also marshaling
stateless programming, 230-32
stored procedures, 8-9, 9
string data type, 119
string parsing, 254-56
structured query language (SQL), 8, 9
stub objects, 70-71, 71, 72
superclasses, 23
surrogate processes, 79-80
synchronization, data, 140-41, 279

T
target journaling, 264-65
Terminate procedure, 189
testing in MTS environment, 195-96
ThreadingModel attribute, 146, 147
thread pooling, 150, 191
threads. See also apartments; multithreading
    and ActiveX DLLs, 147-48
    and ActiveX EXEs, 148-50, 153, 154-55
    and COM+, 155-56
    and concurrency, 140-41
    and data synchronization, 140-41, 279
    and global variables, 151-52
    in MTS, 191-93, 279, 282
    overview, 138-46, 139
    primary, 139
    secondary, 153, 154-55, 154
    thread-per-object vs. thread pool, 150
    user-interface, 139
three-tier architecture
    costs and benefits, 13-14
    defined, 13
    middle-tier services, 293-300
    vs. N-tier architecture, 13, 177
    and RPC, 162-64
TOP END, 209
transactional applications
    and DTC, 209-11
    overview, 207, 208
    steps in running transactions, 208-9
    writing code directly against DTC, 210-11
transactional ASP pages, 288-89
transactional messages, 237-38, 237, 260-64
transactional queues
    creating, 260
    external transactions, 260, 263-64
    internal transactions, 260-63
transaction managers (TMs), 207, 208. See also coordinating transaction manager (CTM); Distributed Transaction Coordinator (DTC); participating transaction manager (PTM)
transaction processing. See online transaction processing (OLTP)
transactions. See also declarative transactions; Microsoft Transaction Server (MTS); MTS transactions; online transaction processing (OLTP)
    ACID rules for, 202, 203-6
    atomic requirement, 202, 203
    committed, 203
    consistency requirement, 202, 203, 214
    and data item lock management, 204-6
    defined, 202
    distributed, 207-11
    durability requirement, 202, 203
    isolation levels, 205-6
    isolation requirement, 202, 204-6
    logical vs. physical, 215
    programming, 206-7
    serializable, 206
    simple, 206-7
Transaction Server type library, 185-87
Transact-SQL, 206, 207
TUXEDO, 207, 209
two-phase commit protocol, 207, 209, 223, 224
two-tier architecture
    adding layer, 10-12, 11, 12
    limitations of, 9-10
    vs. N-tier architecture, 7-14, 177
    overview, 8
    and stored procedures, 8-9, 9
    when to use, 9
type libraries
    defining interfaces in, 109-10
    and enumerations, 95-96
    and IDL, 50
    interface definitions in, 53
    Transaction Server, 185-87
    and Visual Basic, 49, 50, 81-82
TypeOf keyword, 64-65

U
UDT. See user-defined data type (UDT)
universally unique identifiers (UUIDs), 55
universal marshaler, 72, 82, 115, 116, 120-21, 123-24, 125
update locks, 229-30
updating Registry, 196
user accounts, 171-72
user-defined data type (UDT), 120-23, 125
user-defined interfaces
    and automation, 69-70
    and declarative security, 274
    defining in IDL, 110-12
    defining in separate type libraries, 109-10
    vs. MultiUse classes, 108
    overview, 37, 38-39
user-interface threads, 139
UUIDs. See universally unique identifiers (UUIDs)

V
variant data type, 120, 126
VBS array data type, 119-20
VBScript, 283-84, 287-88, 291
VBS string data type, 119
versioning components
    automation clients, 93
    binary, 86-88
    levels of compatibility, 87
    and MTS, 195
    overview, 86
    project compatibility settings, 89-91
    vs. starting from scratch, 93
Visual Basic. See also VBScript
    ActiveX DLLs, 78
    ActiveX EXEs, 78-79
    and automation, 65
    calling built-in ASP objects from, 289-91
    vs. C and C++, 3, 54, 55
    and class factories, 58-59
    COM capabilities, 3
    creating MTS components, 180-82, 189
    creating objects from ASP pages, 286-87
    debugging MTS components, 196, 198-99
    error-handling model, 101, 102-4
    and GUIDs, 55-56
    and IDL, 49, 53-54, 110-12
    and IIS Application Designer, 17
    and implementation inheritance, 23
    integrated development environment, 53, 55, 78, 90, 91
    and interfaces, 20, 30-32, 51-54, 68, 69, 113-14
    and IUnknown interface, 62, 63
    and lifetime management, 63-64
    mapping COM exceptions, 102-4
    mapping to COM, 51-53
    and marshaling, 72, 124-26
    and multithreading, 144, 146-52
    naming conventions, 30
    Object Browser, 186, 290, 290
    persistable classes in, 258-60
    Procedure Attributes dialog box, 96-97
    and RPC, 162
    and threads, 139
    and type libraries, 49, 50, 81-82
    using events, 129-31, 293, 294
    version differences, 52-53
    wizard bar, 32-33, 33
Visual C++, using to debug MTS applications, 196, 197
vTables
    and custom callback interfaces, 134
    defined, 47
    and dual interfaces, 67-68, 68
    and dynamic binding, 47, 47, 69
    and IDispatch interface, 66, 66, 86-88, 131
    and IUnknown interface, 61, 62

W
WAM. See Web application manager (WAM)
Web application manager (WAM), 284, 285
Web-based applications, 283-93
Web classes, 292-93, 292
Web servers, 17, 18, 283
white-box reuse, 27, 28, 29
Win32 API, 43
Win32 threading overview, 139-46
Windows NT
    and COM security, 166, 167-69
    debugging applications with event log, 196, 197
    and distributed development, 14-18
    integration between IIS and MS, 284-85
    security model, 166, 272, 273
    Service Packs for, 260
    setup for MTS, 194-95
    user accounts, 171-72
WithEvents keyword, 130, 131
worker threading, 155-56
write locks, 204-5, 228, 229
WriteProperties method, 258, 259
WriteProperty method, 256

X
X/Open standard, 209