What is sga in oracle 10g

The default value is 0, which means that the IM column store is not used. This initialization parameter must be set to a non-zero value to enable the IM column store. If the parameter is set to a non-zero value, then the minimum setting is M. In a multitenant environment, the setting for this parameter in the root is the setting for the entire multitenant container database CDB.

This initialization parameter can enable tables and materialized views for the IM column store or disable all tables and materialized views for the IM column store. Set this parameter to OFF to specify that all tables and materialized views are disabled for the IM column store. This initialization parameter enables you to specify a default IM column store clause for new tables and materialized views.

Leave this parameter unset or set it to an empty string to specify that there is no default IM column store clause for new tables and materialized views. The clause can include valid clauses for IM column store compression methods and data population options.

This initialization parameter specifies whether in-memory queries are allowed. This initialization parameter specifies the maximum number of background populate servers to use for IM column store population, so that these servers do not overload the rest of the system. Set this parameter to an appropriate value based on the number of cores in the system.

This initialization parameter limits the maximum number of background populate servers used for IM column store repopulation, as trickle repopulation is designed to use only a small percentage of the populate servers. This initialization parameter enables or disables all of the optimizer cost model enhancements for in-memory. Before tables, tablespaces, or materialized views can be enabled for the IM column store, you must enable the IM column store for the database.

Oracle Database Upgrade Guide for information about setting the database compatibility level. Starting Up and Shutting Down. Managing Tables for information about creating and altering tables. The following example enables the oe.

This example enables some columns in the oe. It also specifies different IM column store compression methods for the columns enabled for the IM column store. The following example disables the oe. When a tablespace is enabled for the IM column store, all tables and materialized views in the tablespace are enabled for the IM column store by default. When a tablespace is enabled for the IM column store, individual tables and materialized views in the tablespace can have different in-memory settings, and the settings for individual database objects override the settings for the tablespace.

The following example creates the tbs1 tablespace and enables it for the IM column store:. The following example creates the oe. With this option, Data Pump keeps the IM column store clause for all objects that have one.

For example, you can use this option to change the IM column store compression for a database object being imported. Before you can enable a database to use the IM column store, you must ensure that the database is at a Release You can use the In-Memory Column Store Central Home page to monitor in-memory support for database objects such as tables, indexes, partitions and tablespaces.

You can view in-memory functionality for objects and monitor their In-Memory usage statistics. The In-Memory Object Access Heatmap displays the top objects in the In-Memory Store with their relative sizes and shows you how frequently objects are accessed, represented by different colors.

To activate the heat map, you must turn on the option for the heatmap in the init. Generally there is a one day wait period before the map is activated. You can use the date selector to pick the date range for objects displayed in the Heat Map. You can also use the slider to control the granularity of the color.

Click Edit to navigate to the Initialization Parameters page where you can change the values and settings displayed in this section. Use the Performance section to view the metrics for Active Sessions.

Use the Objects Summary section to view the Compression Factor and data about the memory used by the populated objects. Use the In-Memory Objects Distribution section to view the distribution on a percentage basis of the various objects used in memory. The section includes a chart showing the distribution of Partitions, Sub-partitions, Non-partitioned Tables, and Non-partitioned Materialized Views. The numerical values for each are displayed above the chart.

Click Search after you enter the parameters by which you want to search. You can also search for accessed objects that are either in-memory or not in-memory. If the heatmap is enabled, the Accessed Objects option appears in the drop-down list in the View field of the In-Memory Objects Search box. When you select Accessed Objects, you can filter based on the top objects with access data that are either in-memory or not in-memory. You can select a time range and search for objects within that range.

If you select the All Objects In-Memory option, you can view the list of top objects that are in-memory based on their in-memory size. If you are working in a RAC environment, you can quickly move between instances by selecting the instance in the Instances selection box above and on the right side of the heatmap. The Create Table page is shown. Select the In-Memory Column Store tab to specify the in-memory options for the table. To specify IM column store details for a partition, select it from the table in the Partitions tab, and then click Advanced Options.

Alternatively, you can also click Edit on the Search page. Use the In-Memory Column Store tab to specify in-memory options for the table. The IM column store settings of a tablespace apply for any new table created in the tablespace.

IM column store configuration details must be specified at the individual table level if a table must override the configuration of the tablespace. Automatic memory management is supported only on some platforms. Also, you can query a set of data dictionary views for information on memory management. The following platforms support automatic memory management—the Oracle Database ability to automatically tune the sizes of the SGA and PGA, redistributing memory from one to the other on demand to optimize performance:.

Displays size information about the SGA, including the sizes of different SGA components, the granule size, and free memory. Displays detailed information about how memory is allocated within the shared pool, large pool, Java pool, and Streams pool. Displays information on the current size of all automatically tuned and static memory components, with the last operation for example, grow or shrink that occurred on each.

Displays information about resize operations that are currently in progress. Displays information about dynamic SGA component resize operations that are currently in progress. Note: This view is available starting with Oracle Database 12 c Release 1 Oracle Database Reference for detailed information on memory management views.

Automatic Memory Management. For information about managing memory with Cloud Control, see the Cloud Control online help. See Also: Oracle Database Concepts for an introduction to the various automatic and manual methods of managing memory. Do one of the following: For more complete automatic tuning, set the values of the automatically sized SGA components listed in Table to zero.

To change to ASMM from automatic memory management:. To specify the minimum amount of SGA space for a component: Set a value for its corresponding initialization parameter. To set the lower bound for the size of a component: Set the initialization parameter for the component to the minimum. For example, consider the following configuration:.

Therefore, the rules governing the resizing of all component parameters are the same as in earlier releases. To modify the precise size of a component: Set the initialization parameter for the component. For example, consider this configuration:. To enable manual shared memory management:. You must then set values for the various SGA components, as described in the following sections.

Note: Platform-specific restrictions regarding the maximum block size apply, so some of these sizes might not be allowed on some platforms. A 32K block size is valid only on bit platforms. Note: Multiple buffer pools are only available for the standard block size. See Also: Oracle Database Performance Tuning Guide for information about tuning the buffer cache and for more information about multiple buffer pools.

This parameter cannot be used with automatic memory management. Note: The automatic PGA memory management method applies to work areas allocated by both dedicated and shared server process. See Also: Oracle Database Reference for information about the initialization parameters and views described in this section Oracle Database Performance Tuning Guide for information about using the views described in this section.

Note: This feature is available starting with Oracle Database 12 c Release 1 Note: When an instance is put in force full database caching mode, database objects are not loaded into the buffer cache immediately. Consider adding Database Smart Flash Cache when all of the following conditions are true: Your database is running on the Solaris or Oracle Linux operating systems.

You have spare CPU. Note: You cannot share one flash file among multiple instances. To tune memory for the Database Smart Flash Cache, complete one of the following actions: If you are managing memory manually, then increase the size of the buffer cache by an amount approximately equal to the number of database blocks that fit into the Database Smart Flash Cache as configured, multiplied by or for Oracle RAC.

Note: You can choose to not increase the buffer cache size to account for Database Smart Flash Cache. See Also: " About Memory Management ". For example, assume that your Database Smart Flash Cache uses following flash devices:. See Also: Oracle Database Concepts. Note: A database object that is enabled for the IM column store might not be populated in it.

This method compresses IM column store data the most. Note: The priority level setting must apply to an entire table or to a table partition. To enable the IM column store for a database, complete the following steps:. The minimum setting is M. Hi Tom, You said above "it is reserved, but not touched memory, the OS will not have it physically in ram if you are not using it. April 14, - am UTC. Hi Tom, Thanks for your prompt reply as always. Your replies are always enlightening.

Many thanks for your valuable time. April 23, - am UTC. The OS will do what it feels like doing as far as giving us memory - the OS of today are typically what you might call 'demand paged' - as you demand the memory - they give you the physical memory, paging in from disk if needed.

Typically, with your settings, you would expect to see 1. Same concept applies here, until you actually touch the memory, the OS doesn't have to make it available for you. Thanks for your reply ,Please correct my understaning i it is wrong - 1.

April 23, - pm UTC. Dear All, The basic fundamental behind sizing your SGA System Global Area is nothing comes out on fly, everyone has to have a practical approach rather then getting things easily and readily available.

One cant become a proper DBA just by getting answers on the fly and fix it. So practical approach is very much important. HTH ;. I have no control over the code so I can only tweak the database parameters. December 07, - am UTC. I seriously doubt it. Let me guess: o you are running a connection pool o you have set the connections to cycle themselves every N uses o you set open cursors to to 'fix' an ora the applications would get every now and then In other words, you are trying to mask a massive bug in the client application - they are leaking cursors like a sieve and rather than fix the code, you've made everyone less efficient by hiding the problem and setting parameters really, almost absurdly, high.

I rather think the former however : What is your soft parse percent? Many thanks. February 01, - pm UTC. They are very good - and when I do mention them it is simply to say "use them" They work by using a little bit of extra memory to 'watch' what you have been doing and realistically report drops or increases in physical IO's you can expect to see if you were to follow the advice. February 28, - am UTC. March 02, - am UTC.

Again, my hypothesis is you are using a connection pool, your connections eventually get "max open cursors exceeded" and someone "fixed" it by bumping up the number of open cursors instead of having the developers track down their cursor leak.

Sort of like using a band-aid to fix a leaking pipe, not very pretty and won't last very long. And given that the hard parse rate is so high, that seems to add to my feelings that my hypothesis is correct - the developers are not really in tune with database development if they are hard parsing at such a rate. They are flooding the shared pool with literal sql and leaving cursors open at a relatively high rate. Hi Tom the software comes from the vendor and out of my control I have never had max cursors exceeded.

I have gradually just increased them starting at , incrementing by and now up to over the course of the year. I thought I could keep more sql in the shared pool so it would not have to be swapped out. There were never any erros of any sort. How do you determine just what the max and session cursor should be set at? March 02, - pm UTC. If that session doesn't request that many cursors, it'll never hit it - all you've done is waste a bit of memory on each connection as we use that parameter to size a data structure well, we allocate 64 slots at a time.

You probably should have just left it at the default value, it was more than sufficient. Investigate application logic to keep open the frequently used cursors.

March 08, - pm UTC. You have already found the right size. The only reason I could see for upping open cursors would be to up session cached cursors - but I wouldn't go above or for that setting. Thanks for your time Tom Really appreciate your assistance Jim. September 25, - pm UTC. Ok, it is time for my favorite game: Let's play "guess the question". All you do to play is post some stuff and you let us try to guess what you wanted I'll guess you are using an spfile I'll guess you want to know what your options are Followup December 20, - 8am Central time zone: how true is it?

October 09, - am UTC. You can - but do not technically have to. That is why it is called auto - it is automatic and under the covers. So, it might not be lower, it could be equal. Does this make sense? Buffer hit ratio is Regards Goh. December 17, - am UTC. A gb SGA is becoming fairly "normal" these days. High cpu consumption for simple queries? Tom: I thought on 32 bit machines an oracle instance memory max is 2GB and 64 bit machines it is 4 GB. The larger the cache, the more to manage, the possibly longer the list of blocks to walk.

But gb is not considered huge these days, it is becoming a new normal in some respects. Those 32 bit machine do not scale at all. December 17, - pm UTC. When I started working at Oracle - if your server had MB of ram and 4 cpus which could have been class cpus - the sequent machine I used was - you had a honking big server. When I started at Oracle - the theoretical 1. And you know what - we got stuff done on those machines, believe it - or not.

The world ran on that. Mainframes - they were even smaller memory wise. You can do quite a bit with a 1. But, today in - it wouldn't make sense to use 32bit since 64bit is so widely available. It depends. And it is theoretical, no ones put such a thing together yet - physical machine limits you to a lot less. You have to have engineered a machine capable of having tb of memory. Thanks Tom. Is there any rule of thumb for the buffers chains latching contention event? Appreciate your advice.

December 18, - am UTC. And given that you still do 5million IO's in that IO reads , it doesn't seem to be advisable to reduce the buffer cache this is all off the top of the head here, I don't really know anything about your database I'd doubt that shrinking the SGA would be advisable. It would be a bad idea as it is now. Can share from which section and events that tell no contention of buffer cache latch as explain in your previous reply "you are not really missing your get requests on the latch and not sleeping on it ".

Appreciate it. Tom: I am migrating a 9i schema to 11g R2 new database on linux. Do you normally recommend using the automatic memory manager in 11g or just allocation fixed amount of RAM to use? I heard some DBA saying the memory manager does not work very well and they had to go back to manual mode. May 08, - am UTC. I would use auto pga memory management along with either a sga target with lower bounds set for the db cache, shared pool and such b just setting the db cache, shared pool and such and using the advisors to see if we should schedule a change.

Do i need to do something special in dbca or after db is created to set minimum buffer cache size or anything else. May 10, - am UTC. Sam have your DBA take care of this please. I'm asking since I'm not really sure where this cache is stored or if it's even in the SGA.

Thanks for all the help over the years! I appreciate that the DB is better at managing its data than OS filesystem caching, but in future any DBA who demands more memory on the grounds "more is better" will be asked to show some evidence that the application needs it.

To digress slightly, and give you a view from the "other side" - Many years ago, I went on a Unix performance tuning course. And he was right, most issues I've seen since then could only be slightly helped by hardware or OS tweaking, whereas a review of indexes or SQL gave huge improvements.

But I'll browse the rest of "AskTom" to get your views on these side issues. Size of the database is about gb. I am trying to prove to client that the huge SGA is causing the latches and paging to occur. Let me know your advice, or the points I need to look for to highlight that indeed the large SGA is cauising this. Thanks, Praveen. May 07, - pm UTC. The number one cause of the sympton - artificially high concurrency. The OS would tell you that.

Tom, First of all, thank you very much for spending your valuable time in helping people like me. We are so blessed. I am trying to calculate the estimated size of SGA. Please provide some guidance. Thanks for your help. July 01, - pm UTC. What happen if SGA memory is very low? Kumaraswamy, June 29, - am UTC. Hi Tom, what will happen if SGA's allocated memory is very low apart from it's performance? Please tell me how else we can make an educated guess for the correct parameters. Wondering if there is a way at all apart from the advisory.

A reader, December 09, - am UTC. There are some duplicate acronyms that may be problematic because it is not clear which component is being used. Feel free to ask questions on our Oracle forum. Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise.

All legitimate Oracle experts publish their Oracle qualifications. Oracle technology is changing and we strive to update our BC Oracle support information. Shared memory file systems for the SGA are covered at Section The SGA attach address does not have to be changed for that.