Hello Sanjay, > i had one big OLTP environment running on Solaris 10 with 256G RAM and 30+ > CPU. > There are sometime in a day when all OS command are totally freezed. > Even ls command take several minute. CPU was showing more than 60% idle. > If I am connected to database, then call to check Db like locks or other > query works fine. > What can be the issue to be checked more closely. > Also Application trying to connect from outside are affected. Since your on Solaris 10, you have access to DTrace [1]. If you or one of the Solaris systems administrator is familiar with this tool, then I'd suggest you give it a try. DTrace helps troubleshoot problems on servers by providing new detailed views of the system internals, to a level that was previously difficult to access. Using both truss(1M) and dtrace(1M), one would hope that you can pin-point your problem. A quick search for dtrace turned out two books [2] [3] and several links to blogs and articles, the personal DTrace website [4] of one of the authors, Bendan Gregg. And the official Oracle page on DTrace [5]. HTH, David [1] http://en.wikipedia.org/wiki/DTrace [2] DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD (Oracle Solaris Series) by B. Gregg and J. Mauro, Prentice Hall; 1 ed., April 11, 2011, ISBN-13: 978-0132091510 [3] Solaris Performance and Tools: DTrace and MDB Techniques for Solaris 10 by B. Gregg, J. Mauro and R. McDougall, Prentice Hall; 1 ed., July 30, 2006, ISBN-13: 978-0131568198 [4] http://www.brendangregg.com/dtrace.html [5] http://www.oracle.com/technetwork/systems/dtrace/dtrace/index.html -- David Robillard UNIX team leader and Oracle DBA LinkedIn http://www.linkedin.com/in/davidrobillard Blog http://itdavid.blogspot.com/ -- //www.freelists.org/webpage/oracle-l