Skip to main content

Database for Hard Real time Systems

Databases for real time systems are meant for the use of both hard and soft systems. Since hard real time systems needs strict timing constraints, conventional disk based databases are not suitable, but soft real time systems makes use of disk based systems through FCFS, Elevator or scan policy algorithm.

There should be some solution for Hard Real time systems with high performance and guaranteed response time constraints. MDARTS (Multiprocessor Database Architecture for Real Time System) is one such main memory database which uses VME based processors.

Features


  • This is for Hard Real time Systems

  • It is a main memory database (the entire database resides on the main memory)

  • Object oriented database (C++ elements)

  • Supports explicit declaration of real time constraints and semantic constraints within the application code.
    Constraints Specifications
    Access time ”write <=80usec ; read<=50usec” Staleness ”stale<=20msec” Persistence ”volatile”

  • The above are the constraints which can be included in the application code directly without the recompilation of the MDARTS library.

  • Supports direct, concurrent, shared memory data access.

Shared Memory Objects



  • This is suitable for NGC (Next generation Workstation/machine controller) for automated factories
  • The timing constraints of some real time applications are such that database transactions on the order of tens of microseconds may be needed
  • The above diagram shows the access to the data from the shared memory
  • The control task is periodic with hard deadline every msec. Each time the control task runs, it extracts the current sensor values from the database and computes new control signals for the actuators.
  • Data accessed extremely high speed must be stored in the physical shared memory as the virtual memory and disk based databases may generate the page faults which should not be generated for main memory.
  • Applications need not know whether the database access is local or remote. The database handler hides the information of being remote. Remote access achieved through Remote Procedure calls (RPC). There may be some communication delay when the data is accessed remotely.
  • The shared data manager (SDM) tracks the location and identity of the shared memory objects and also constructs its own database handle for each object to service remote requests.

Comments

Popular posts from this blog

Installing TexLive 2019 in Ubuntu 18.04

Installation of TexLive 2019 in Linux (Ubuntu 18.04 LTS)
TeX (Tech)

Installation of TexLive 2019

Please watch the video for full installation



I used .iso file to download, the Total size is 3.3GB for Linux,

and i used the torrent file to download, it took me just 20 min to download the entire .iso file

Extract the .iso file to a folder and open a terminal

$] sudo ./install-tl
(it goes into a terminal mode, which is faster compared to the GUI Mode)

$] sudo ./install-tl -gui
after the installation, set the PATH, MANPATH and INFOPATH as suggested by LATEX

export PATH=$PATH:/usr/local/texlive/2019/bin/x86_64-linux
export MANPATH=/usr/local/texlive/2019/texmf-dist/doc/man
export INFOPATH=/usr/local/texlive/2019/texmf-dist/doc/info

put these lines in to the /home/pradeepkumar/.bashrc

$] gedit /home/pradeepkumar/.bashrc
We have installed TexLive 2019 and texstudio.

To install texstudio

$] sudo apt install texstudio
The look and feel of TexStudio looks like this image.


texlive, it install everyt…

Implementing a new system call in Kernel version 2.6.32

A system call is used by application or user programs to request service from the operating systems. Since the user programs does not have direct access to the kernel whereas the OS has the direct access. OS can access the hardware through system calls only.The following files has to be modified for implementing a system call/usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S/usr/src/linux-2.6.32.5/arch/x86/include/asm/unistd_32.h/usr/src/linux-2.6.32.5/include/linux/syscalls.h/usr/src/linux-2.6.32.5/MakefileNew set of files to be createdCreate a new directory newcall/ inside the path “/usr/src/linux-2.6.32.5/” Create new files Makefile, newcall.c and put them in the /usr/src/linux-2.6.32.5/newcall/ folder Create new user files (in any folder of Linux) to test the system call
testnewcall.c, testnewcall.h (created in /home/pradeepkumar) syscall_table_32.S Find the file /usr/src/linux-2.6.32.5/arch/x86/kernel/syscall_table_32.S and add the following line at the end
"…

Electrical Machine Design (equations)

FactorsDC Machine Transformers Induction Machines Synchronous MachinesOutput EquationPa=CoD2Ln, where Pa=P/h for generators, Pa=P for motorsFor Single Phase
Q=2.22 f Bm Ai Kw Aw d10-3
For Three Phase
Q=3.33 f Bm Ai Kw Aw d 10-3Q=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * hQ=CoD2 L ns
KVA Input Q=
HP * 0.746 / Cos f * h
For Turbo alternators
Q=1.11Bavac KwsVa2 L 10-3/nsOutput CoefficientCo=Bav ac* 10-3where Bav-magnetic loading and ac - electric loadingDNACo=11 Kws Bav ac 10-3Co=11 Kws Bav ac 10-3 Choice of Magnetic LoadingFlux Density in Teeth Frequency of Flux Reversals Size of machineDNAMagnetizing current, Flux Density, Iron lossIron loss, Stability, Voltage Rating, Parallel Operation, Transient ShortCircuit current Choice of Electric LoadingTemperature rise,
speed of machine, Voltage, Armature reaction, CommutationDNAOverload Capacity, Copper losses, Temperature rise, Leakage ReactanceCopper loss, Synchronous reactance, Temperature rise, Stray Load losses,
Voltage rating Flux …