IBM OS/390 User Manual

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At the physical level, in DB2 each tablespace is stored in a pageset, which
consists of one or multiple VSAM ESDS data sets or LDSs. In SQL/DS, data is
stored in storage pools that are composed of one or more dbextents. In VSE, a
dbextent consists of one VSAM ESDS data set. While this may seem similar, the
difference is that in DB2 one VSAM data set is used for only one tablespace. In
SQL/DS, one VSAM data set can be used to store data from any or all tables in
the system (within one storage group).
As a result of the different storage structures and names used, a new physical
data model must be developed for the DB2 environment and then the
parameters associated with storage structures in the data definition language
(DDL) SQL statements must be updated to implement the new physical data
model.
8.2.1.5 Security Administrators
Both products have the same set of table privileges (ALTER, DELETE, INDEX,
INSERT, REFERENCES, SELECT and UPDATE). Other privileges related to the use
of resources (such as using space by creating table) and operation (such as
executing programs) are granted in a similar manner, but the definition of user
types is different. Thus, there are different operands within the GRANT
command. DB2 allows group authorization (not in SQL/DS, but in the new
Control Center feature of DB2/VSE V5) so that fewer GRANT statements need to
be issued.
Implementation is different in how users are given certain authority and each
product has its own naming convention. Because the two products differ in how
databases are defined and organized, the levels of authorization are more robust
in DB2. In DB2, the highest level authority is called SYSADM and in SQL/DS, the
equivalent level is called DBA. Some noteworthy differences in the SQLs are:
The VSE CONNECT statement can have 
user IDENTIFIED BY password
″, 
but
the OS390 can not.
Tables on VSE can specify CCSIDs at the column level. Current (for
DB2/OS390 V5) CCSIDs can only be specified at the table level. So if the VSE
customer is utilizing this, they will need to convert their data to use a
common CCSID in the table.
When DB2 is installed, only users with SYSADM authority have the SELECT
privilege on catalog tables. With SQL/DS, upon initial install all users have
SELECT privilege on catalog tables. In DB2, SYSADM and other users granted
the proper authority can update catalog statistics used by the optimizer in
access path selection. In SQL/DS, DBA authority includes all table privileges on
catalog tables. The tables in the catalog are organized differently in the two
products. Therefore, catalog queries will be incompatible between the two.
8.2.2 Other Comparison Areas
8.2.2.1 Year 2000
DB2 for OS/390 Version 5 is Year 2000 compliant. For DB2 for MVS/ESA Versions
3 and 4, you need to apply an APAR for Year 2000 compliance. For more details,
get the DB2 and the Year 2000 White Paper from the Web. Its URL is:
Chapter 8. Databases
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