If I recall correctly (it's been 15 years since I last played an Oracle DBA) ... and correct me if I'm wrong ...
Oracle has several processes that run at the OS level, eg, a listener, database management threads, user management threads, licensing thread, etc, etc, etc.
When you shutdown an Oracle database, some of those other OS processes are left up and running, eg, the listener.
sqlplus connects to the listener process and through various options you can use this connection to 'start up' an Oracle database.
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With Sybase you have a single OS process called a dataserver (in UNIX/Linux the executable/binary is actually called 'dataserver'). This single OS process ('dataserver') has embedded in it a lot of the same functionality as the various Oracle processes, eg, listener, database management, user management, licensing, security, etc, etc, etc ... plus some OS-like features, eg, thread/process scheduler, process run queues, memory management, etc.
A Sybase dataserver manages several databases including system databases (eg, master, sybsystemdb, tempdb, sybsystemprocs) as well as application specfiic databases (eg, saptools, SAP SID specific databases, etc). To access any of these databases the user (or application) must first connect to the dataserver and then once connected can then access the various databases managed by the dataserver.
isql connects to the dataserver through the dataserver's internal listener thread.
If the dataserver is down then so are all of the threads/processes that normally run inside of the dataserver, including the listener. Also, *all* databases managed by the dataserver are offline/not-accessible. So, if the dataserver is down, then the listener thread is also down, so isql has nothing to connect to.
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A Sybase dataserver is typically started by running what's called a RUNSERVER file (in UNIX/Linux this is a small shell script; in Windows it's a small *bat file, though in Windows it's more common to have a Windows Service defined for starting/stopping a Sybase dataserver).
The RUNSERVER file is normally located under the $SYBASE/ASE-XX_X/install directory and has a name like 'RUN_<name_of_dataserver>'. A basic, bare bones RUNSERVER shell script will include a call of the 'dataserver' binary along with several command line options (eg, name of dataserver, location of config file, location of errorlog, etc).
Starting up a Sybase dataserver typically consists of executing the RUNSERVER file.
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NOTE: While I've worked with Sybase ASE for ~23 years, I do not work with SAP applications so fwiw ...
You mention that you can start up Sybase by running 'startsap'. 'startsap' is a SAP specific program which I'm assuming is either a shell script or a binary that, among other things, executes the RUNSERVER file. Alternatively it could call the dataserver binary directly. (I'm sure one of the SAP knowledgeable folks can chime in here if more details are needed.)
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You've used some terminology that can be a bit confusing in a Sybase environment.
While it is possible to shutdown (or take offline) a Sybase *database*, this is more of an advanced topic. Instead we usually refer to shutting down the dataserver (which in turn means all databases managed by the dataserver are taken offline and become unavailable).
By default, when starting up a Sybase dataserver, all databases managed by the dataserver are also brought online/made-available.
While it is possible to start up a dataserver and only bring certain databases online, or in a special case only bring the 'master' database online, these fall (again) under the heading of advanced topics. Instead we usually refer to starting up the dataserver and then waiting for the dataserver to bring all of its databases online for general access.
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When you mention "how to start it again master database alone", I'm assuming you are *not* talking about starting the Sybase dataserver and bringing only the 'master' database online but rather ... you're trying to bring up the Sybase dataserver without bringing up the associated SAP application.
In this case I'd suggest you take a look at the RUNSERVER script (RUN_<SID> ?). If this script exists you should be able to run it as its owner. [Again, SAP knowledgeable folks can step in here if there's a different method for starting up the Sybase dataserver without starting the SAP application.]
Once the dataserver is up and running, and its databases are online, you should be able to log into the dataserver (eg, with isql) and access the various databases managed by the dataserver.
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If the above doesn't provide you with the details you're looking for then I'll echo Johan's recommendation ... provide more details on what you're trying to do. For example:
- Is the dataserver process up and running at the OS level? (ps -aef | egrep dataserver)
- Can you successfully connect to the dataserver with isql? (if not, what options are you providing to isql and what error(s) are you getting?)
- If you can successfully connect to the dataserver via isql, are all of your databases online? (see output from 'sp_helpdb')