user63569: I'm just not understanding what does the following arguments do! 
-dbcache : Set database cache size in megabytes (4 to 16384, default: 300)

which database is that? and what may happen if the file size excessed
  16384 megabytes.

-par=N  Set the number of script verification threads (-2 to 16, 0 = auto, <0 = leave that many cores free, default: 0)

What is script verifications threads? may this affect performance? 

-pid= Specify pid file (default: bitcoind.pid)

what is this for?

-bind=    Bind to given address and always listen on it. Use [host]:port notation for IPv6

is this for RPC calls, so bitcoin core listens only to given IP address?

-discover   Discover own IP addresses (default: 1 when listening and no -externalip or -proxy)

what do they mean? 

-upgradewallet  Upgrade wallet to latest format on startup


what is the wallet formats?

-rpcbind=<addr> Bind to given address to listen for JSON-RPC connections. Use [host]:port notation for IPv6. This option can be specified multiple times (default: bind to all interfaces)


when we Bind to IP address, will the software listens to this IP address only? 

-rpcthreads=<n> Set the number of threads to service RPC calls (default: 4)


how many connections can a thread afford? and how the connections counted? is it per IP address or command? 


user38482: -dbcache: bitcoin is doing heavy disk I/O, you can reduce disk I/Os with increasing this parameter and thus increase memory usage
-par: if your system is so slow, you can't use it anymore, limit the number of threads or CPU/cores that are used
-pid: this is usually the process ID on your unixoide system. if you start a single instance, there is nothing to play with...
-bind: if you have several network cards in your system, you can bind the process to one of the many IP addresses in your system
-discover: discover IP addresses in the network. Set to 1, else set to 0, e.g. if you are using connections over TOR. 
-upgradewallet: - someone else please :-)
-rpcbind: if your system is multihomed, and you want to talk from several networks to your machine, you can tell the bitcoin daemon, to listen to only a specific address for remote procedure calls
-rpcthreads: 

how many connections can a thread afford?  

good question, I don't know. Experts please. I was of the opinion, that one thread can handle one connection... 

and how the connections counted?

not sure what you mean by this - if you have 4 clients, that connect to your system, then you have 4 connections. Or 5... or 6 ... and you can have 4 different systems talk to your bitcoind.

is it per IP address or command?

per IP address.
I know my answer is not 100%, so I am asking for additional help as well. 

63569: <p>I'm just not understanding what does the following arguments do! </p>

<p>-dbcache : Set database cache size in megabytes (4 to 16384, default: 300)</p>

<blockquote>
  <p>which database is that? and what may happen if the file size excessed
  16384 megabytes.</p>
</blockquote>

<p>-par=N  Set the number of script verification threads (-2 to 16, 0 = auto, &lt;0 = leave that many cores free, default: 0)</p>

<blockquote>
  <p>What is script verifications threads? may this affect performance? </p>
</blockquote>

<p>-pid= Specify pid file (default: bitcoind.pid)</p>

<blockquote>
  <p>what is this for?</p>
</blockquote>

<p>-bind=    Bind to given address and always listen on it. Use [host]:port notation for IPv6</p>

<blockquote>
  <p>is this for RPC calls, so bitcoin core listens only to given IP address?</p>
</blockquote>

<p>-discover   Discover own IP addresses (default: 1 when listening and no -externalip or -proxy)</p>

<blockquote>
  <p>what do they mean? </p>
</blockquote>

<pre><code>-upgradewallet  Upgrade wallet to latest format on startup
</code></pre>

<blockquote>
  <p>what is the wallet formats?</p>
</blockquote>

<pre><code>-rpcbind=&lt;addr&gt; Bind to given address to listen for JSON-RPC connections. Use [host]:port notation for IPv6. This option can be specified multiple times (default: bind to all interfaces)
</code></pre>

<blockquote>
  <p>when we Bind to IP address, will the software listens to this IP address only? </p>
</blockquote>

<pre><code>-rpcthreads=&lt;n&gt; Set the number of threads to service RPC calls (default: 4)
</code></pre>

<blockquote>
  <p>how many connections can a thread afford? and how the connections counted? is it per IP address or command? </p>
</blockquote>
 38482: <p>-dbcache: bitcoin is doing heavy disk I/O, you can reduce disk I/Os with increasing this parameter and thus increase memory usage</p>

<p>-par: if your system is so slow, you can't use it anymore, limit the number of threads or CPU/cores that are used</p>

<p>-pid: this is usually the process ID on your unixoide system. if you start a single instance, there is nothing to play with...</p>

<p>-bind: if you have several network cards in your system, you can bind the process to one of the many IP addresses in your system</p>

<p>-discover: discover IP addresses in the network. Set to 1, else set to 0, e.g. if you are using connections over TOR. </p>

<p>-upgradewallet: - someone else please :-)</p>

<p>-rpcbind: if your system is multihomed, and you want to talk from several networks to your machine, you can tell the bitcoin daemon, to listen to only a specific address for remote procedure calls</p>

<p>-rpcthreads: </p>

<blockquote>
  <p>how many connections can a thread afford?  </p>
</blockquote>

<p>good question, I don't know. Experts please. I was of the opinion, that one thread can handle one connection... </p>

<blockquote>
  <p>and how the connections counted?</p>
</blockquote>

<p>not sure what you mean by this - if you have 4 clients, that connect to your system, then you have 4 connections. Or 5... or 6 ... and you can have 4 different systems talk to your bitcoind.</p>

<blockquote>
  <p>is it per IP address or command?</p>
</blockquote>

<p>per IP address.</p>

<p>I know my answer is not 100%, so I am asking for additional help as well. </p>
