RE: (forte-users) Serialisation

Question

Singh,
Any message sent across partition boundaries is serialized. This includes
method invokations, events and exceptions. The signature of the message
itself is serialized, as well as the values of all parameters/attributes.
Serializing a scalar value requires less overhead then serialising an
object, however, the difference isn't as big as you might think. Objects
have more attributes then just the value you're interested in and these
attributes are serialised as well. Each object is an instance of a class and
each class has a UUID, which is added to the serialized stream as well.
However, methods are NOT serialised. What happens is this. Forte serializes
an object into a stream containing only the values of the attributes
(including nested attributes). This stream is given a header which sais of
which class this object is an instance (the UUID is used for that). The
receiving partition reads the serialized stream, finds the definition of the
class (defined by UUID) in its own code, creates an instance of this class
and fills the data out of the serialized stream into this new object.
You can imagine what might happen if there is a mismatch between the
class-definitions in both partitions. You either get
serialization-deserialization errors, or the receiving partition complains
that it doesn't even know the UUID of the received streamed object, or you
get no errors at all and just have an object that displays different
behaviour, depending what partition it's in.
If there are no problems, then the main issue is the
serializing-deserializing overhead. Note that the receiving partition has to
instantiate a new object for every serialized object it receives and will
therefore execute all code in the Init() method. This overhead is not
required for scalar types, for which Forte only needs to reserve a small
amount of memory space on the stack.
Any call to a database is also a message sent across partitions and is
therefore serialized. However, one partition is a Forte partition and the
other one isn't. Therefore, Forte's internal serialization mechanism isn't
used. Forte serializes the SQL-query into a format understood by the
database (which is different for every vendor). Forte then receives a stream
back which has a different format for every different database type. This
stream is deserialized and written to attributes that Forte has reserved to
contain the data. Whether these are scalar, datavalues or domains only
impacts performance inside the Forte partition. It has no effect on the
communication with the database.
Pascal Rottier
Atos Origin Nederland (BAS/West End User Computing)
Tel. [phone]
Fax. [phone]
E-mail: Pascal.Rottiernl.origin-it.com
++++++++++++++++++++++++++++
Philip Morris (Afd. MIS)
Tel. [phone]
Fax. [phone]
E-mail: Rottier.Pascalpmintl.ch
-----Original Message-----
From: Singh [mailto:fortelistyahoo.com]
Sent: Thursday, February 22, 2001 3:30 AM
To: forte-userslists.xpedior.com
Subject: (forte-users) Serialisation
Hello All
I have a question that has been bugging me for some
time.
We all know that it is better to use scalar data
types, as opposed to objects, when passing data across
a network.
The reason, if I understand correctly, is that when
you send an object across a network, the whole object
(properties, attributes and methods) is deserialised
into zero's and one's before being sent across and
then serialised back into the object when it gets to
the other side. This would take longer for an object
since for a scalar value, just the value is
deserialised and serialised.
But when you are writing to a database from the tier
before the database to the database, does it matter
what type you use. The reason for saying this is that
the values are serialised before they go across and
then deserialised when they get to the base, in other
words, they are sent as zero's and one's. For a scalar
- just the value is sent across but for an object -
does just the value go across or the complete object.
If just the value of the object goes across, then it
doesn't really matter whether a scalar or object is
sent across.
Am I correct in this assumption.
Thanks in advance for your help.
Regards,
Singh
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Answer 1

Hi,
I cannot get hold of Tech Note 10398..... can anyone email me a copy?
Tx
Etienne
-----Original Message-----
From: Klerk, Theo de [SMTP:Theo.de.Klerkcompaq.com]
Sent: Wednesday, February 09, 2000 4:26 PM
To: 'Jason de Cean'; 'Forte Users'
Subject: RE: (forte-users) Serialisation
There are a number of flags that will show you some of the required
information in a log file (not within the application itself). Technote
10398 has many more flags listed for a variety of obscure, useful, not so
useful and exotic information:
trc:cm:*:4 and *:8 - show packet serialisation, open, closes between
partition communication
trc:do:*:2 - proxy creation/deletion, exception events
trc:do:*:5 - individual message tracing between proxies
trc:do:*:8 - serialisation information
Theo
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