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Access remote data via VSAM Redirector |
The VSAM Redirector is a new VSE function in the category VSE as client. It enables a VSE/VSAM application to access data on a remote system. The VSE program doesn't need any change. Working with a remote relational database (i.e. IBM DB2 UDB), a real time synchronization between VSAM data and the database can be done. The same function can be used on VSE locally, as exit for data collection (e.g. incremental FTP), or as an exit for Journaling. The function is transparent for batch or CICS programs
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Overview |
The VSAM Redirector function is based on the VDA Exit (VSAM Data Access Exit) in VSAM. The VSAM Redirector function intercepts VSAM requests and forwards them for further processing. On VSE, a configuration table needs to be set up in order to define which VSAM files are being redirected.
VSAM requests can be redirected to:
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a local exit in VSE (EXIT=EXITNAME) for further additional processing of a request. This function can be used for example to collect all changes of a file in a separate VSAM cluster for incremental work.
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a remote system (EXIT=IESREDIR). On the remote system the VSAM request is then translated into i.e. database commands.
The VSAM Redirector function consists of two components:
With the option called OWNER, the decision can be made whether:
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OWNER=VSAM: VSAM data should be synchronized with the database. That means every write request will be executed for VSAM and the database with two phase commit. Read requests are done from VSAM only.
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OWNER=REDIRECTOR: The program should work with the remote database only. That means no VSAM data is processed anymore - it is a transparent work of a VSAM program with a remote database.
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Benefits |
This functionality opens new dimensions of integration of VSE/VSAM programs with remote data especially with remote relational databases.
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VSE programs can work without any change with remote data.
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Real time synchronization between VSAM and a relational database with two phase commit.
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For FTP modernization, the cumulative changes during a certain period can be collected and transferred instead of transferring whole files.
Once the data resides in a database, the data can be accessed by many kinds of applications:
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Web applications
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Data warehousing
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Reporting tools
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Software requirements |
The following software requirements must be meet in order to implement this solution:
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VSE/ESA 2.6 or later
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VSAM Redirector configured on VSE
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Linux, Windows, AIX, Unix on remote system
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How to get started |
To redirect VSAM requests (from batch or CICS applications) the following steps must be done:
For the VSE side:
- Decide upon the VSAM files to be redirected and the remote system where they should be redirected to.
- Decide upon the record structure (i.e. COBOL or PL/I copy book ) that defines the destination structure of the data in the database.
- Corresponding entries in the configuration phase (skeleton SKRDCFG in ICCF Lib 59) must be defined. The configuration can be changed multiple times, it becomes active at OPEN time of a VSAM file. Changing the configuration for an OPENED VSAM file, requires a CLOSE/OPEN to that file to activate the new configuration.
On the remote platform:
- Define the database that will host the VSAM data.
- The information about the mapping structure of VSAM records to a relational table will be stored in a second table separate from the data.
- Use the create tool delivered in VSAM Redirector server to create the tables for the data and the mapping definitions of the VSAM file.
To migrate an entire VSAM file to the database, an additional VSAM file has to be defined with the same structure as the original one (clone). The second file will be set up to be redirected in the configuration phase. Now a simple IDCAMS REPRO can copy the original file to the redirected one. That means all data will be copied to the destination database table. Once that's done, the original file will be set up to be redirected and up to that time all requests will be redirected to the database - for synchronization or redirected access.
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Additional information |
Additional information for this solution scenario can be found:
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