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home/Knowledge Base/Oracle Database/Oracle Tuning/Linux Free Command Usage
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Linux Free Command Usage

178 views 0 September 5, 2019 admin

Linux Free Command Usage For Oracle DBA

Display amount of free and used memory in the system.

The shared memory column should be ignored; it is obsolete.

  • total – Your total, physical (assuming no virtualization) memory
  • used – How much of that is currently used (by anything)
  • free – How much of that is completely free (not used at all)
  • shared – (never anything there, ignore that column)
  • buffers – Memory used by kernel buffers
  • cached – Memory used for cache

Default output for free command is in Kilobytes.

Syntax :

free options

free [-b | -k | -m] [-o] [-s delay ] [-t] [-l] [-V]

Options:

  • The -b switch displays the amount of memory in bytes; the -k switch (set by default) displays it in kilobytes; the -m switch displays it in megabytes.
  • The -t switch displays a line containing the totals.
  • The -o switch disables the display of a “buffer adjusted” line. If the -o option is not specified, free subtracts buffer memory from the used memory and adds it to the free memory reported.
  • The -s switch activates continuous polling delay seconds apart. You may actually specify any floating point number for delay,
  • The -l switch shows detailed low and high memory statistics.
  • The -V switch displays version information.

Files to see memory information:

/proc/meminfo

Examples:

1. Free command with option -b, display the size of memory in Bytes.

2. Free command with option -m, display the size of memory in megabytes.

3. Free command with option -g, display the size of memory in gigabytes.

4. Free command with -t option, will list the total at the end.

5. The -s option with number, used to update free command at regular intervals.

6. The -l option displays detailed high and low memory size statistics.

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