DB2 users’ patience tested with extended wait for Version 2 Release 3
IBM says that DB2 Version 2 Release 3 is the next step in the delivery SAA distributed relational database management. The new version extends access to relational data distributed between DB2 systems under MVS and Structured Query Language/Data system under VM, regardless of where the data is located. The DB2 implementation of remote-unit-of-work support based on the distributed relational database management architecture permits access to relational databases in either SAA or non-SAA systems that fully implement that architecture. However, the base functions won’t be available until October 25, 1991, and IBM says that availability date of the remote-unit-of-work distributed database management functions will not even be announced until September 30, 1991. With MVS 4.2, APPC/MVS applications can access data managed by DB2 through the DB2 call attachment facility and the DB2 TSO attachment facility. For releases of DB2 prior to Version 2 Release 3, an assembler H program module is required between the call attachment facility and application programs written in PL/I, Fortran, VS Cobol, VS Cobol II and C. DB2 also supports Data Propagator MVS/ESA which can be used to update DB2 tables automatically when corresponding information in the DL/1 database is updated. IMS data propagated to DB2 is accessible to the SQL/DS VM users through distributed data.
System and Database Administration
DB2 can bind an application program into smaller packages that can be used by more than one application, and it also provides the ability to maintain multiple versions of the same program, the choice of which version to execute and which objects are accessed. The CICS execution diagnostic facility enables programmers to test applications without modifying code or preparation procedure, and it will also show information from the database request module which contains information about SQL statements. A new option provides users with the choice of which DB2 catalogue tables the Runstats utility will update with statistical information about tables, table spaces and indexes. The two classes are those used by DB2 to optimise the performance of SQL statements, or those used by database administrators to asses the status of a perticular table space or index. Interactive panels permit the user to look at information in the DB2 catalogue without composing queries, and the Diagnose utility permits the user to be more specific when choosing the type of dumps to be produced. DB2 internal sorting is said to be improved in the MVS/ESA environment by enhancements to ES/9000 Models 190 and above, the 9000-T models, and the 180J, 200J, 280J and above. SQL statements that use sorting for ordering may complete faster, and the same applies to indexing. The number of rows can be specified in an SQL statement, and DB2 has an op-tion to hold cursors in Commit statements, but not in the CICS transaction environment.
Enhanced DB2 Systems Management
New functions said to aid management and use of local and distributed data include DB2’s remote unit of work which enables the use of data definition and data manipulation languages. Secondly, the resource limit facility, which enables a system administrator to control the amount of resources used by dynamic queries, has been enhanced to enable the administrator to determine whether whether a bind request will be run. Authorisation enhancements are included for for local and distributed database management, and DB2 now offers support for secondary authorisation identifications for remote data access. IBM says that DB2 also offers several major enhancements to make recovery quicker, and several of those apply to recovering at a separate site from an unplanned total shutdown. With the improved Copy utility, up to four image copies can be created simultaneously, two for the local database management systems, and two for the recovery database management systems. The Recovery facility has been speeded up and multiple index partitions on a table can be
recovered simultaneously.
DB2 Access and Distribution
Access from one DB2 subsystem to another was available in Version 2 Release 2, and that has been extended to enable access between DB2 in MVS/ESA and MVS/XA environments and SQL/DS in the VM/SP Release 6 and VM/ESA environments. IBM says that the new release is the next step in providing distributed database management support across the four SAA environments – MVS, VM, AS/400 and PS/2 OS/2 Extended Edition. The distributed remote-unit-of-work permits access to a single remote relational database management subsystem within a unit of work consisting of several SQL statements. The remote database management subsytem processes the statements and updates the database when all the statements have been completed. An application program can access data from tables within a unit of work so long as the tables reside in a single database management system. A Time Sharing Application can read and update data in one database, either local or remote, within a unit of work, and an IMS or CICS transaction reads data from the local database in a single unit of work.
Improvements to user numbers, data sets and columns
The maximum number of concurrent users is increased from 220 to 2,000, and the maximum number of columns allowed for a DB2 table is also increased to 750 from 300. The composition of DB2 index keys is extended from 16 to a maximum of 64 columns, and the number of datasets is raised to 10,000 although MVS/SP 3.1.0 or 3.1.3 and DFP 3.2 are required.
Security and control features
DB2 uses the security features of its host systems MVS/XA and MVS/ESA systems, and it protects its resources by controlling system access, data access and control, concurrent access, and data recovery and accounting.
