ObjectScript provides a toolkit for synchronizing objects of selected types between namespaces
containing compatible type classes. The core of the synchronization toolkit is the SyncSet. A
SyncSet contains all of the objects of selected types that have been filed in the local database
from a defined starting time up to an ending time. "Time" in the context of synchronization means
a sequencing value and is not an "hours-minutes-seconds" value.
Object Synchronization consists of three primary tasks. The first task is to build the SyncSet.
That task involves determining which objects are to included in the SyncSet. %SYNC uses a transaction
journal for that purpose. The transaction journal is implemented as %Library.ObjectJournalTransaction.
Any persistent or serial class that declares the class parameter OBJJOURNAL as true will record all
filing events in %Library.ObjectJournalTransaction.
The second task is to add changed objects to the SyncSet. The most common mechanism for performing this
task is to retrieve the object state from the system journal using information recorded in %Library.ObjectJournalTransaction.
This mechanism allows historical object data to be included in the SyncSet. If the system journal is
not available, there is a provision to include the current object state.
The third task is to import the SyncSet into the namespace being synchronized. This involves loading the
SyncSet global into the target namespace and then importing each object contained in the SyncSet. If an object
being imported already exists in the target namespace then the timestamp for the imported object
is compared to the timestamp of the existing object. If a conflict is detected then user implemented code
is called to resolve the conflict. This is essentially an optimistic concurrency mechanism. If the conflict
is not resolved successfully then a concurrency error is reported and the object is not synchronized.
This is a string value used to identify the Sync Set object. This value is used as the suffix
to the global name root of ^OBJ.SYNC.. For example, if the sId is
set to the integer 1 then the global name will be ^OBJ.SYNC.1.
Add an object to the current SyncSet. This method can be used to force an object to be included in the
SyncSet when it isn't recorded in the ObjectJournal. It should not be used for normal situations since
the ObjectJournal is expected to be complete. Normally, an object that is added to the SyncSet is a
versioned object meaning that the object state is recovered from history (normally, from the system
journal). AddObject causes the object as it currently exists in the extent to be added to the SyncSet, breaking
the natural chronology of the SyncSet.
class - the object's type class;
id - the object's ID value;
fileop - the filing operation that caused this object to be added to the sync set
0 - update
1 - insert
2 - delete
guid - the object's GUID
Add %Library.ObjectJournalTransactions to the current SyncSet. Each transaction in the %ObjectJournalTransaction extent is identified
by an integer that is incremented for each new transaction. This ID assignment mechanism places transactions in chronological order, that is,
the order in which the transactions are created. Transactions are expected to be in that order when later imported and sync'ed into another
namespace. This method adds a range of transactions, beginning with iTranLast and ending with iTranEnd. The TNumber
argument, if specified and is not zero, limits the number of transactions added. When that number of transactions has been added the method will
return to the caller, even if the iTranEnd value has not yet been reached.
The LastTransaction property is set to the ID of the last transaction added to the SyncSet.
method Clear() as %Status [ Language = objectscript ]
This method should be used for data removal when the syncset is no longer needed. It deletes all the persistent data
and makes impossible further usage of the object.
classmethod CollectionValuesClose(ByRef qHandle As %Binary) as %Status [ Language = objectscript ]
classmethod CollectionValuesExecute(ByRef qHandle As %Binary, sid As %String = "0", iObjPtr As %Integer = 0, CollName="") as %Status [ Language = objectscript ]
classmethod CollectionValuesFetch(ByRef qHandle As %Binary, ByRef Row As %List, ByRef AtEnd As %Integer = 0) as %Status [ Language = objectscript ]
method ErrCount() as %Integer [ Language = objectscript ]
classmethod ErrorsClose(ByRef qHandle As %Binary) as %Status [ Language = objectscript ]
classmethod ErrorsExecute(ByRef qHandle As %Binary, sid As %String = "0") as %Status [ Language = objectscript ]
classmethod ErrorsFetch(ByRef qHandle As %Binary, ByRef Row As %List, ByRef AtEnd As %Integer = 0) as %Status [ Language = objectscript ]
This method synchronizes each object contained in the sync set with the current database. Each object is first checked for concurrency.
Concurrency conflicts occur when the object is modified on the local system after the object was last synchronized with the remote system
where the sync set originated. If a concurrency conflict is detected, the object is passed to the %ResolveConcurrencyConflict
method in %Library.SwizzleObject. If the conflict cannot be resolved, the object is requeued for later
processing and the concurrency error is reported in the %%SERR error log. Otherwise, the object is synchronized by passing it to the
%SyncObjectIn method in %Library.SwizzleObject.. If the synchronization fails, then the object is requeued for
There are two types of common synchronization errors. The first is an unresolved dependency. This type of error occurs when an object
references another object and the referencing property is part of a REQUIRED constraint. That means the object cannot be saved
until the reference can be resolved. This problem is often caused by a reference to an object that is in the sync set but has not yet been processed. The second
type of problem is an unresolved reference. This type of problem occurs in the same was as an unresolved dependency but the reference is not required in order
for the object to be saved. An object with an unresolved reference is partially synchronized and only the reference is requeued for later processing.
Once all of the objects in the sync set have been processed, the Import method attempts to synchronize all objects that were requeued. During this phase,
all of the unresolved dependencies and references are expected to be resolved. Any objects that fail to synchronize during this phase are left in an
unresolved state. Unresolved objects and errors reported during synchronization can be accessed by using the Unresolved query
or the Errors query.
When all of the objects contained in the Sync Set have been processed the time stamps in the %SYNC.SyncTime class are updated using
the maxTS value.
The name of a file containing a sync set. If a file name is specified, then that file will be loaded into the global.
If no file is specified, then the global is expected to already exist in the current namespace.
An integer value indicating the SyncTime value when this System.Namespace was last
synchronized with the System.Namespace that generated the sync set being imported. If this value is not
specified, then it will be retrieved from %SYNC.SyncTime
The highest transaction ID contained in the sync set. It is used to set the rTrn property
in the %SYNC.SyncTime class. This value is not used for any purpose during import and is
maintained for informational purposes only. This value is specified by the user and is expected to be
the ID of the last %Library.ObjectJournal object included in the sync set.
See the %SYNC.SyncTime for more information on the rTrn and lTrn properties.
Option flags. This formal argument is maintained for backward compatibility only.
Array of errors encountered during import. These are not errors encountered during synchronization but are
errors reported doing tasks like opening the file.
If true, then Import will display status information on the current device.
If true, then Import will record all import activity in the sync set global under the "Trace" subscript.
method IsEmpty() as %Boolean [ Language = objectscript ]
method OpenFile(file As %String = "", qspec As %String = "", ByRef errorlog) as %Status [ Language = objectscript ]
Open a file containing a sync set global and load it into the current sync set global.
Files containing sync set globals are typically in GOF format and are produced by exporting
a sync set on another system.
classmethod PropertyValuesClose(ByRef qHandle As %Binary) as %Status [ Language = objectscript ]
classmethod PropertyValuesExecute(ByRef qHandle As %Binary, sid As %String = "0", iObjPtr As %Integer = 0) as %Status [ Language = objectscript ]
classmethod PropertyValuesFetch(ByRef qHandle As %Binary, ByRef Row As %List, ByRef AtEnd As %Integer = 0) as %Status [ Language = objectscript ]
Return the pointer to the next unresolved object.
This is only valid if Import() has been run to completion before calling
this method and ..UnresolvedFirst() has been called to initialize the unresolved object
method nextPointer(ByRef iTranPtr, ByRef iTranLast) [ Language = objectscript ]