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Mainframe learnings

http://en.wikipedia.org/wiki/CICS
CICS: is a transaction server supporting facilities like transaction, i/o db access, db access etc. Its fucntion can be likened to an J2EE application server...the advantage lies in speed as it works on legacy mainframes. it also support distributed transaction processing, standard rpc type stuff(eg EXEC CICS LINK command)...though through proprietary methods...

EXEC CICS is an API--that has a whole suite of commands available

VSAM is essentially a record based file system. As cobol data is essentially records, this can be considered as a virtual database type filesystem. (?) the internals of the filesystem are unclear http://en.wikipedia.org/wiki/VSAM

cics for windows supports c/c++ too and has header and lib files to compile programs.Note, In CICS Transaction Server for Windows, argc is always set to
1, argv[0] contains the transaction code, and argv[1] is null.

CICS resources referes to files, programs etc available on the filessytem.


It provides for 'maps' or map sets which

?
CICS transaction
CICS program


This brings us to the point on why mainframes are fasters...which is covered later


-----------------Copy Paste-----------------
Virtual Storage Access Method (VSAM) is an IBM disk file storage scheme first used in the OS/VS2 operating system and later used throughout the MVS architecture. VSAM comprises four access methods: Key Sequenced Data Set (KSDS), Relative Record Data Set (RRDS), Entry Sequenced Data Set (ESDS) and Linear Data Set (LDS). See record-oriented filesystem.

VSAM records can be of fixed or variable length. They are organised in fixed-size blocks called Control Intervals (CIs), and then into larger divisions called Control Areas (CAs). Control Interval sizes are measured in bytes — e.g. 4K — while Control Area sizes are measured in disk tracks or cylinders.

The program IDCAMS is commonly used to manipulate ("delete and define") VSAM datasets. Custom programs can access VSAM datasets through data definitions (DD's) in Job Control Language (JCL) or in online regions such as CICS (Customer Information Control Systems.)

Both IMS/DB and DB2 are implemented on top of VSAM and use its underlying data structures.

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Programs that include EXEC CICS commands are processed by the
appropriate command-language translator, which translates these commands
into programming language statements. You compile and link your translated
program in the usual way. When your program is executed, the statements
inserted by the translator invoke the API server module (FAASRSML). This
provides the service requested by a command by invoking one or more CICS
control programs.

----------------------

Transfer of control between programs, using the EXEC CICS XCTL and
EXEC CICS LINK commands. All called programs must contain an EXEC
CICS RETURN command.

---------------------

The ability to start CICS transactions and to call CICS programs from
external (non-CICS) programs running either on a server or on a client
using the following features:
External transaction initiation (ETI)
External presentation interface (EPI)
External call interface (ECI)
-----------------

Storage control
Each transaction is restricted to the storage it owns. The application fails if it
attempts to refer to other storage. If a program uses an EXEC CICS GETMAIN
command to allocate other storage areas, this storage is allocated as private,
and therefore cannot be shared by other transactions.
If you need to use shareable storage, use the EXEC CICS GETMAIN SHARED
command.
Temporary storage queues are held on disk, that is, in auxiliary storage, even
if the MAIN option is specified on the EXEC CICS WRITEQ TS command.

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