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Operating Systems HP-UX Performance problem - waiting on cache Post 302489785 by ctsgnb on Friday 21st of January 2011 03:43:22 PM
Old 01-21-2011

Oracle Database 10g runs I/O operations from both shared memory and process-private regions using the new HP-UX asynchronous driver. However, I/O operations through the asynchronous driver are not asynchronous in nature. This is because Oracle Database must perform a blocking wait to check the status of I/O operations submitted to the asynchronous driver. This causes some Oracle processes, such as the database writer process, to essentially process synchronous I/O.

This is an extract from this link

seems like asynchronous I/O on HP-UX with Oracle is only supported for raw FS

How many DB writer are currently set up on your DB ?

Few considerations about it you might want to prefer:

a) the FS type hosting the datafile can handle async I/O (oracle param DISK_ASYNCH_IO = true) so the DB writer can let the OS deal with the update (without having to do "wait" events)

b) if your FS type doesn't support async I/O you can setup more than 1 DBWR (DBWR_PROCESSES/db_writer_processes) but since the oracle buffer cache is divided in as much working sets, you might want to adjust the DB_BLOCK_LRU_LATCHES.

c) Last solution, activate the forking to simulate asynch I/O by activating the use of slave processes (DBWn_IO_SLAVES) which are in fact synchronous I/O (DISK_ASYNCH_IO = false). Risks of that last solution are buffer overhead, wait, memory overhead (IPCs & context switch)

Last edited by ctsgnb; 01-21-2011 at 05:16 PM..
 

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DBIx::SearchBuilder::Handle::Oracle(3pm)		User Contributed Perl Documentation		  DBIx::SearchBuilder::Handle::Oracle(3pm)

NAME
DBIx::SearchBuilder::Handle::Oracle - An oracle specific Handle object SYNOPSIS
DESCRIPTION
This module provides a subclass of DBIx::SearchBuilder::Handle that compensates for some of the idiosyncrasies of Oracle. METHODS
Connect PARAMHASH: Driver, Database, Host, User, Password Takes a paramhash and connects to your DBI datasource. BuildDSN Customized version of "BuildDSN" in DBIx::SearchBuilder::Handle method. Takes additional argument SID. Database argument used unless SID provided. Two forms of DSN are generated depending on whether Host defined or not: dbi:Oracle:sid=<SID>;host=...[;port=...] dbi:Oracle:<SID> Read details in documentation for DBD::Oracle module. Insert Takes a table name as the first argument and assumes that the rest of the arguments are an array of key-value pairs to be inserted. InsertFromSelect Customization of "InsertFromSelect" in DBIx::SearchBuilder::Handle. Unlike other DBs Oracle needs: o id generated from sequences for every new record. o query wrapping in parens. NOTE that on Oracle there is a limitation on the query. Every column in the result should have unique name or alias, for example the following query would generate "ORA-00918: column ambiguously defined" error: SELECT g.id, u.id FROM ... Solve with aliases: SELECT g.id AS group_id, u.id AS user_id FROM ... KnowsBLOBs Returns 1 if the current database supports inserts of BLOBs automatically. Returns undef if the current database must be informed of BLOBs for inserts. BLOBParams FIELD_NAME FIELD_TYPE Returns a hash ref for the bind_param call to identify BLOB types used by the current database for a particular column type. The current Oracle implementation only supports ORA_CLOB types(112). ApplyLimits STATEMENTREF ROWS_PER_PAGE FIRST_ROW takes an SQL SELECT statement and massages it to return ROWS_PER_PAGE starting with FIRST_ROW; DistinctQuery STATEMENTREF takes an incomplete SQL SELECT statement and massages it to return a DISTINCT result set. BinarySafeBLOBs Return undef, as Oracle doesn't support binary-safe CLOBS DatabaseVersion Returns value of ORA_OCI constant, see "Constants" in DBI. SimpleDateTimeFunctions Returns hash reference with specific date time functions of this database for "DateTimeFunction" in DBIx::SearchBuilder::Handle. ConvertTimezoneFunction Custom implementation of "ConvertTimezoneFunction" in DBIx::SearchBuilder::Handle. Use the following query to get list of timezones: SELECT tzname FROM v$timezone_names; Read Oracle's docs about timezone files: http://download.oracle.com/docs/cd/B14117_01/server.101/b10749/ch4datetime.htm#i1006667 AUTHOR
Jesse Vincent, jesse@fsck.com SEE ALSO
perl(1), DBIx::SearchBuilder perl v5.14.2 2011-09-21 DBIx::SearchBuilder::Handle::Oracle(3pm)
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