Siebel on Sun CMT hardware : Best Practices

The following suggested best practices are applicable to all Siebel deployments on CMT hardware (Tx00, T5x20, T5x40) running Solaris 10 [Note: some of this tuning applies to Siebel running on conventional hardware running Solaris]. These recommendations are based on our observations from the 14,000 user benchmark on Sun SPARC Enterprise T5440. Your mileage may vary.

All Tiers
  • Ensure that the system's firmware is up-to-date.

  • Upgrade to the latest update release of Solaris 10.

      Note to the customers running Siebel on Solaris 5/08: apply the kernel patch 137137-07 as soon as it is available on web site. Patch 137137-07 and later revisions, Solaris 10 10/08 will have the workaround to a critical Siebel specific bug. Oracle Corporation will eventually fix the bug in their codebase - in the meantime Solaris is covering for Siebel and all other 32-bit applications with their own memory allocators that return unaligned mutexes. Check the RFE 6729759 Need to accommodate non-8-byte-aligned mutexes and Oracle's Siebel support document 735451.1 Do NOT apply Kernel Patch 137111-04 on Solaris 10 for more details.

  • Enable 256M large pages on all nodes. By default, the latest update of Solaris 10 will use a maximum of 4M pages even when 256M pages are a good fit.

      256M pages can be enabled with the following /etc/system tunable.
      \* 256M pages
      set max_uheap_lpsize=0x10000000

  • Pro-actively avoid running into stdio's 256 file descriptors limitation.

      Set the following in a shell or add the following lines to the shell's profile (bash/ksh).
      ulimit -n 2048
      export LD_PRELOAD_32=/usr/lib/$LD_PRELOAD_32

      Technically the file descriptor limit can be set to as high as 65536. However from the application's perspective, 2048 is a reasonable limit.

  • Improve scalability with MT-hot memory allocation library, libumem or libmtmalloc.

    To improve the scalability of the multi-threaded workloads, preload MT-hot object-caching memory allocation library like libumem(3LIB), mtmalloc(3MALLOC).

      eg., To preload the libumem library, set the LD_PRELOAD_32 environment variable in the shell (bash/ksh) as shown below.

      export LD_PRELOAD_32=/usr/lib/$LD_PRELOAD_32

      Web and the Application servers in the Siebel Enterprise stack are 32-bit. However Oracle 10g or 11g RDBMS on Solaris 10 SPARC is 64-bit. Hence the path to the libumem library in the PRELOAD statement differs slightly in the database-tier as shown below.

      export LD_PRELOAD_64=/usr/lib/sparcv9/$LD_PRELOAD_64

    Be aware that the trade-off is the increase in memory footprint -- you may notice 5 to 20% increase in the memory footprint with one of these MT-hot memory allocation libraries preloaded. Also not every Siebel application module benefits from MT-hot memory allocators. The recommendation is to experiment before implementing in production environments.

  • TCP/IP tunables

    Application fared well with the following set of TCP/IP parameters on Solaris 10 5/08.

    ndd -set /dev/tcp tcp_time_wait_interval 60000
    ndd -set /dev/tcp tcp_conn_req_max_q 1024
    ndd -set /dev/tcp tcp_conn_req_max_q0 4096
    ndd -set /dev/tcp tcp_ip_abort_interval 60000
    ndd -set /dev/tcp tcp_keepalive_interval 900000
    ndd -set /dev/tcp tcp_rexmit_interval_initial 3000
    ndd -set /dev/tcp tcp_rexmit_interval_max 10000
    ndd -set /dev/tcp tcp_rexmit_interval_min 3000
    ndd -set /dev/tcp tcp_smallest_anon_port 1024
    ndd -set /dev/tcp tcp_slow_start_initial 2
    ndd -set /dev/tcp tcp_xmit_hiwat 799744
    ndd -set /dev/tcp tcp_recv_hiwat 799744
    ndd -set /dev/tcp tcp_max_buf  8388608
    ndd -set /dev/tcp tcp_cwnd_max  4194304
    ndd -set /dev/tcp tcp_fin_wait_2_flush_interval 67500
    ndd -set /dev/udp udp_xmit_hiwat 799744
    ndd -set /dev/udp udp_recv_hiwat 799744
    ndd -set /dev/udp udp_max_buf 8388608

Siebel Application Tier
  • All T-series systems (T1000/T2000, T5120/T5220, T5120/T5240, T5440) support the 256M page size. However Siebel's siebmtshw script restricts the page size to 4M. Comment out the following lines in $SIEBEL_HOME/siebsrvr/bin/siebmtshw.
      # This will set 4M page size for Heap and 64 KB for stack

  • Experiment with less number of Siebel Object Managers.

      Configure the Object Managers in such a way that each OM will be handling at least 200 active users. Siebel's standard recommendation of 100 or less users per Object Manager is suitable for conventional systems but not ideal for CMT systems like Tx000, T5x20, T5x40, T5440. Sun's CMT systems are ideal for running multi-threaded processes with tons of LWPs per process. Besides, there will be significant improvement in the overall memory footprint with less number of Siebel Object Managers.

  • Try Oracle 11g R1 client in the application-tier. Oracle 10g R2 clients may crash under high load. For the symptoms of the crash, check Solaris/SPARC: Oracle 11gR1 client for Siebel 8.0.

      Oracle 10g R2 32-bit client is supposed to have a fix for the process crash issue - however it wasn't verified in our test environment.

Siebel Database Tier
  • Eliminate double buffering by forcing the file system to use direct I/O.

    Oracle database caches the data in its own cache within the shared global area (SGA) known as the database block buffer cache. Database reads and writes are cached in block buffer cache so the subsequent accesses for the same blocks do not need to re-read the data from the operating system. On the other hand, file systems on Solaris default to reading the data though the global file system cache for improved I/O operations. That is, by default each read is cached potentially twice - one copy in the operating system's file system cache, and the other copy in Oracle's block buffer cache. In addition to double caching, there is also some extra CPU overhead for the code which manages the operating system's file system cache. The solution is to eliminate double caching by forcing the file system to bypass the OS file system cache when reading and writing to the disk.

      In the 14,000 user benchmark setup, the UFS file systems (holding the data files and the redo logs) were mounted with the forcedirectio option.

      mount -o forcedirectio /dev/dsk/<partition> <mountpoint>

  • Store data files separate from the redo log files -- If the data files and the redo log files are stored on the same disk drive and if that disk drive fails, the files cannot be used in the database recovery procedures.

      In the 14,0000 user benchmark setup, there are two Sun StorateTek 2540 arrays connected to the T5440 - one array was holding the data files, where as the other was holding the Oracle redo log files.

  • Size online redo logs to control the frequency of log switches.

      In the 14,0000 user benchmark setup, two online redo logs were configured each with 10 GB disk space. When all 14,000 concurrent users are on-line, there is only one log switch in a 60 minute period.

  • If the storage array supports the read-ahead feature, enable it. When 'read-ahead enabled' is set to true, the write will be committed to the cache as opposed to the disk, and the OS signals the application that the write has been committed.

    Oracle Database Initialization Parameters

  • Set Oracle's initialization parameter DB_FILE_MULTIBLOCK_READ_COUNT to appropriate value. DB_FILE_MULTIBLOCK_READ_COUNT parameter specifies the maximum number of blocks read in one I/O operation during a sequential scan.

      In the 14,0000 user benchmark configuration, DB_BLOCK_SIZE was set to 8 kB. During the benchmark run, the average reads are around 18.5 kB per second. Hence setting DB_FILE_MULTIBLOCK_READ_COUNT to a high value does not necessarily improve the I/O performance. A value of 8 for the database init parameter DB_FILE_MULTIBLOCK_READ_COUNT seems to perform better.

  • On T5240 and T5440 servers, set the database initialization parameter CPU_COUNT to 64. Otherwise, by default Oracle RDBMS assumes 128 and 256 for the CPU_COUNT on T5240 and T5440 respectively. Oracle's optimizer might use a completely different execution plan when it notices such a large number for the CPU_COUNT; and the resulting execution plan need not necessarily be an optimal one. In the 14,000 user benchmark, setting CPU_COUNT to 64 produced optimal execution plans.

  • On T5240 and T5440 servers, explicitly set the database initialization parameter _enable_NUMA_optimization to FALSE. On these multi-socket servers, _enable_NUMA_optimization will be set to TRUE by default. During the 14,000 user benchmark run, we noticed intermittent shadow process crashes with the default behavior. We didn't realize any additional gains either with the default NUMA optimizations.

Siebel Web Tier
  • Upgrade to the latest service pack of Sun Java Web Server 6.1 (32-bit).

  • Run the Sun Java Web Server in multi-process mode by setting the MaxProcs directive in magnus.conf to a value that is greater than 1. In the multi-process mode, the web server can handle requests using multiple processes with multiple threads in each process.

      When you specify a value greater than 1 for the MaxProcs, the web server relies on the operating system to distribute connections among/between multiple web server processes. However many modern operating systems including Solaris do not distribute connections evenly, particularly when there are a small number of concurrent connections.

  • Tune the maximum simultaneous requests by setting the RqThrottle parameter in the magnus.conf file to appropriate value. A value of 1024 was used in the 14,000 user benchmark.

Great tuning info, although I think the $ symbols got eaten in the LD_PRELOAD_XX examples (such as export LD_PRELOAD_64=/usr/lib/sparcv9/ versus export LD_PRELOAD_64=/usr/lib/sparcv9/$LD_PRELOAD_64)

Posted by William Hathaway on October 13, 2008 at 12:46 AM PDT #

My understanding is that LD_PRELOAD expects whitespace-separated values, not colon-separated. Are you sure your examples are correct?

Posted by Darius Terrell on March 08, 2012 at 03:36 PM PST #

Darius: I know that colon-separated syntax works. You can experiment with both colon-separated values as well as white space-separated values on any Solaris box. Once the process is started with the LD_PRELOAD* env variable(s) set, check the output of "pldd <pid>" to see if the libraries
specified in LD_PRELOAD are loaded into the process address space.

Posted by Giri Mandalika on March 08, 2012 at 03:48 PM PST #

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