{ "date": "2016-06-16T17:48:18", "slug": "large-pages-on-windows", "link": "https://www.dbi-services.com/blog/large-pages-on-windows/", "title": { "rendered": "Large Pages on Windows" }, "content": { "rendered": "

By Franck Pachot

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ORA_LPENABLE

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To let Oracle use Large Pages on Windows, you need to define a registry string ORA_LPENABLE=1. This will enable large pages for all instance so it’s probably better to do it at instance level with ORA_SID_LPENABLE, especially if you have an ASM instance on your server. Note that large pages is a recommandation for an database server but if you have other applications that use lot of memory you may lack of memory because of fragmentation.

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Stopping the service:

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\nC:\\cygwin64\\bin>net stop OracleServiceCDB\nThe OracleServiceCDB service is stopping.\nThe OracleServiceCDB service was stopped successfully.\n
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Showing the registry:

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\nC:\\cygwin64\\bin>reg query HKLM\\Software\\Oracle\\Key_OraDB12Home1\n \nHKEY_LOCAL_MACHINE\\Software\\Oracle\\Key_OraDB12Home1\n    ORACLE_HOME    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\n    ORACLE_HOME_NAME    REG_SZ    OraDB12Home1\n    ORACLE_GROUP_NAME    REG_SZ    Oracle - OraDB12Home1\n    NLS_LANG    REG_SZ    AMERICAN_AMERICA.WE8MSWIN1252\n    ORACLE_BUNDLE_NAME    REG_SZ    Enterprise\n    OLEDB    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\\oledb\\mesg\n    ORACLE_HOME_TYPE    REG_SZ    1\n    ORACLE_SVCUSER    REG_SZ    oracle\n    ORACLE_SVCUSER_PWDREQ    REG_SZ    1\n    ORACLE_BASE    REG_SZ    C:\\app\\oracle\n    MSHELP_TOOLS    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\\MSHELP\n    ORACLE_HOME_KEY    REG_SZ    SOFTWARE\\ORACLE\\KEY_OraDB12Home1\n    SQLPATH    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\\dbs\n    RDBMS_CONTROL    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\\DATABASE\n    RDBMS_ARCHIVE    REG_SZ    C:\\app\\oracle\\product\\12.1.0\\EE12101\\DATABASE\\ARCHIVE\n    ORA_CDB_AUTOSTART    REG_EXPAND_SZ    TRUE\n    ORA_CDB_SHUTDOWN    REG_EXPAND_SZ    TRUE\n    ORA_CDB_SHUTDOWNTYPE    REG_EXPAND_SZ    immediate\n    ORA_CDB_SHUTDOWN_TIMEOUT    REG_EXPAND_SZ    90\n    ORACLE_SID    REG_SZ    CDB\n    ORA_LPENABLE    REG_SZ    1\n \nHKEY_LOCAL_MACHINE\\Software\\Oracle\\Key_OraDB12Home1\\ODE\nHKEY_LOCAL_MACHINE\\Software\\Oracle\\Key_OraDB12Home1\\OLEDB\n
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Starting the service:

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C:\\cygwin64\\bin>net start OracleServiceCDB\nThe OracleServiceCDB service is starting...\nThe OracleServiceCDB service was started successfully.
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and tailing the alert.log:

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C:\\cygwin64\\bin>adrci exec=\"set home cdb ; show alert -tail 5\"\n2016-06-13 12:51:22.709000 -07:00\nArchiving is disabled\n2016-06-13 12:51:32.153000 -07:00\nInstance shutdown complete\n2016-06-13 12:51:38.179000 -07:00\nStarting ORACLE instance (normal) (OS id: 1620)\nCLI notifier numLatches:3 maxDescs:519\nLarge page enabled. Mode is : 1\nLarge page size            : 2097152\nLarge page request size    : 16777216\n2016-06-13 13:00:38.599000 -07:00\nStarting ORACLE instance (normal) (OS id: 1760)\nCLI notifier numLatches:3 maxDescs:519\nLarge page enabled. Mode is : 1\nLarge page size            : 2097152\nLarge page request size    : 16777216\n2016-06-13 13:01:37.707000 -07:00\nStarting ORACLE instance (normal) (OS id: 1888)\nCLI notifier numLatches:3 maxDescs:519\nLarge page enabled. Mode is : 1\nLarge page size            : 2097152\nLarge page request size    : 16777216
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You can see my registry entries on the right and the alert.log on the left.

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\"CaptureWCLP001\"

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But this is not sufficient to start the instance:

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\"CaptureWCLP003\"

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Lock pages in memory

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In 12c you can, and you should, run the Oracle Database instance as another user than the system administrator.
\nLarge pages must be locked in physical memory (and that’s one good reason to use them) but by default non administrators do not have this privilege.

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You have to allow it with the Local Goup Policy Editor. Unfortunately, doing that in a Windows Server Core seems to be very difficult because gpedit-msc is not there.

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At that point, my enthousiasm for Windows Core ended and I installed Windows Server GUI.

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\"VirtualBox_Windows

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Now I can startup. Here is the alert.log:

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\nStarting ORACLE instance (normal) (OS id: 2620)\nWed Jun 15 09:53:12 2016\nCLI notifier numLatches:7 maxDescs:519\nWed Jun 15 09:53:12 2016\nLarge page enabled. Mode is : 1\nWed Jun 15 09:53:12 2016\nLarge page size            : 2097152\nLarge page request size    : 16777216\nWed Jun 15 09:53:12 2016\nAllocated Large Pages memory of size :         14680064 \nWed Jun 15 09:53:12 2016\nAllocated Large Pages memory of size :       1660944384 \nLICENSE_MAX_SESSION = 0\nLICENSE_SESSIONS_WARNING = 0\nInitial number of CPU is 4\nNumber of processor cores in the system is 4\nNumber of processor sockets in the system is 1\nPicked latch-free SCN scheme 3\nUsing LOG_ARCHIVE_DEST_1 parameter default value as USE_DB_RECOVERY_FILE_DEST\nAutotune of undo retention is turned on. \nIMODE=BR\nILAT =51\nLICENSE_MAX_USERS = 0\nSYS auditing is enabled\nNOTE: remote asm mode is local (mode 0x1; from cluster type)\nNOTE: Using default ASM root directory ASM\nOracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production\nWith the Partitioning, OLAP, Advanced Analytics and Real Application Testing options.\nWindows NT Version V6.2  \nCPU                 : 4 - type 8664, 4 Physical Cores\nProcess Affinity    : 0x0x0000000000000000\nMemory (Avail/Total): Ph:5718M/8191M, Ph+PgF:7735M/10111M \n
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And yes, I am in Automatic Memory Management (AMM) where size of PGA and SGA is dynamically resized by Oracle within MEMORY_TARGET:

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\nUsing parameter settings in server-side spfile C:\\APP\\ORACLE\\PRODUCT\\12.1.0\\DBHOME_1\\DATABASE\\SPFILECDB.ORA\nSystem parameters with non-default values:\n  processes                = 300\n  use_large_pages          = \"ONLY\"\n  memory_target            = 1600M\n  control_files            = \"C:\\APP\\ORACLE\\ORADATA\\CDB\\CONTROL01.CTL\"\n  control_files            = \"C:\\APP\\ORACLE\\FAST_RECOVERY_AREA\\CDB\\CONTROL02.CTL\"\n  db_block_size            = 8192\n  compatible               = \"12.1.0.2.0\"\n  db_recovery_file_dest    = \"C:\\app\\oracle\\fast_recovery_area\"\n  db_recovery_file_dest_size= 500M\n  _catalog_foreign_restore = FALSE\n  undo_tablespace          = \"UNDOTBS1\"\n  remote_login_passwordfile= \"EXCLUSIVE\"\n  db_domain                = \"\"\n  dispatchers              = \"(PROTOCOL=TCP) (SERVICE=CDBXDB)\"\n  audit_file_dest          = \"C:\\APP\\ORACLE\\ADMIN\\CDB\\ADUMP\"\n  audit_trail              = \"DB\"\n  db_name                  = \"CDB\"\n  open_cursors             = 300\n  diagnostic_dest          = \"C:\\APP\\ORACLE\"\n  enable_pluggable_database= TRUE\n
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On Windows, all Oracle “processes” run as threads of the same Windows process, I don’t see any reason to advise against AMM there.
\nNote that I don’t see any reason to recommend it either…

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Update 20-JUN-2016

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My Oracle Support engineer has confirmed that there is no problem to use AMM with large pages on windows systems. Doc ID 422844.1 -“Using Large Memory Pages on 64-Bit Windows Systems” confirms that large pages are used only for SGA, not PGA, so only SGA is locked in memory and 2MB pages. However, I think it’s a good idea to set SGA_TARGET to get a minimum that keeps allocated because frequent resizing may lead to fragmentation. And if you want to allocate small pages when large pages are not available, you can set ORA_LPENABLE=2 since 12c.

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Added 18th December 2016

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My tests (see http://dbi-services.com/blog/large-pages-and-memory_target-on-windows/) show that it’s not a good idea to mix AMM and Large Pages even on Windows, and this is why I deleted the previous update. Oracle developers have confirmed that we should avoid AMM with Large Pages.

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