Ans: SQLNET users will show up with a process unique name that begins with oracle, if you do a ps -ef|grep oracle|wc -l you can get a count of the number of users.

Ans: The ps command prints the process status for some or all of the running processes. The information given is the process identification number (PID), the amount of time that the process has taken to execute so far etc.

Ans: It reads the standard input and sends it to the standard output while redirecting a copy of what it has read to the file specified by the user.

Ans: Cat, more, pg.

Ans: If the disk block descriptor does not contain any record of the faulted page, then this causes the attempted memory reference is invalid and the kernel sends a? Segmentation violation? Signal to the offending process. This happens when the swapping system identifies any invalid memory reference.

Ans: chmod command is used to change file permission syntax: chmod category operation permission filename where category may be u = user ,g = group = others, a = all operation may be '+' = assign permission,'-' = remove permission,'=' = exact permission may be r=read,w=write=execute: $chmod a+x file1 (give execute permission of file1 to all).

Ans: When Kernel swaps the process out of the primary memory, it performs the following:
Kernel decrements the Reference Count of each region of the process. If the reference count becomes zero, swaps the region out of the main memory, Kernel allocates the space for the swapping process in the swap device. Kernel locks the other swapping process while the current swapping operation is going on. The Kernel saves the swap address of the region in the region table.

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Kernal: It carries out basic operating system functions such as allocating memory, accessing files and handling communications.

Shell: A shell provides the user interface to the Kernal. There are 3 major shells: C-shell, Bourne shell, Korn shell.

Ans: A Map is an Array, which contains the addresses of the free space in the swap device that are allocatable resources, and the number of the resource units available there.

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• It decides which process should reside in the main memory.
• Manages the parts of the virtual address space of a process which is non-core resident.
• Monitors the available main memory and periodically write the processes into the swap device to provide more processes fit in the main memory simultaneously.