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value of a static initonly field must be determined before the JIT compiler resolves the field To achieve this, NET comes with a new construct called a type initializer According to the CLI specification, a type initializer is called by the runtime at or before first access of any static field of that type (For details on the timing guarantees for type initialization, please refer to the documentation on the beforefieldinit modifier in the CLI specification) Type initializers are sometimes called static constructors because many NET languages, including C++/CLI and C#, allow you to define a type initializer with a constructor-like syntax.barcode font excel, barcode add in for word and excel 2013, barcode generator excel 2010 free, install barcode font excel 2007, free 2d barcode generator excel, how to create a barcode in microsoft excel 2007, barcode generator excel 2016, how to print barcodes in excel 2010, barcode erstellen excel freeware, creating barcode in excel 2010,
The cost model of the Optimizer takes into account both I/O cost and CPU cost, both in units of time. The CBO evaluates alternate query costs by comparing the total time it takes to perform all the I/O operations, as well as the number of CPU cycles necessary for the query execution. The CBO takes the total number of I/Os and CPU cycles that will be necessary according to its estimates, and converts them into execution time. It then compares the execution time of the alternative execution paths and chooses the best candidate for execution. For the CBO to compute the cost of alternate paths accurately, it must have access to accurate system statistics. These statistics, which include items such as I/O seek time, I/O transfer time, and CPU speed, tell the Optimizer how fast the system I/O and CPU perform. It s the DBA s job to provide these statistics to the Optimizer. I show how to collect system statistics in the following section.
Although Oracle can automatically collect Optimizer statistics for you regarding your tables and indexes, you need to collect operating system statistics with the GATHER_SYSTEM_STATS procedure. When you do this, Oracle populates the SYS.AUX_STATS$ table with various operating system statistics, such as CPU and I/O performance. Gathering system statistics at regular intervals is critical, because the Oracle CBO uses these statistics as the basis of its cost computations for various queries. System statistics enable the Optimizer to compare more accurately the I/O and CPU costs of alternative execution. The Optimizer is also able to figure out the execution time of a query more accurately if you provide it with accurate system statistics.
The effect of this is to echo the original contents of the file, minus any commented lines (those beginning with #). The sed output is piped into an awk one-liner that filters out lines of length 0. The resulting sequence is a quick way to remove all blank and commented entries of a file.
You can run the GATHER_SYSTEM_STATS procedure in the following modes: No workload mode: By using the NOWORKLOAD keyword, you can collect certain system statistics. These statistics mostly pertain to general I/O characteristics of your system, such as I/O seek time and I/O transfer speed. You should ideally run the GATHER_SYSTEM_STATS procedure in the no workload mode right after you create a new database. The procedure takes only a few minutes to complete. Workload mode: To collect representative statistics such as CPU and I/O performance, you must collect system statistics during a specified interval that represents a typical workload for your instance. You can use the INTERVAL keyword to specify statistics collection for a certain interval of time. You can alternatively use the START and STOP keywords to collect system statistics for a certain length of time. IOTFRSPEED: I/O transfer speed (bytes per millisecond) IOSEEKTIM: Seek time + latency time + operating system overhead time (milliseconds) SREADTIM: Average time to (randomly) read a single block (milliseconds) MREADTIM: Average time to (sequentially) read an mbrc block at once (milliseconds) CPUSPEED: Average number of CPU cycles captured for the workload (statistics collected using the INTERVAL or START and STOP options) CPUSPEEDNW: Average number of CPU cycles captured for the no workload mode (statistics collected using NOWORKLOAD option) MBR: Average multiblock read count for sequential read, in blocks MAXTHR: Maximum I/O system throughput (bytes/second) SLAVETHR: Average slave I/O throughput (bytes/second) Here s the syntax of the GATHER_SYSTEM_STATS procedure: DBMS_STATS.GATHER_SYSTEM_STATS gathering_mode VARCHAR2 interval INTEGER stattab VARCHAR2 statid VARCHAR2 statown VARCHAR2 ( DEFAULT DEFAULT DEFAULT DEFAULT DEFAULT 'NOWORKLOAD', NULL, NULL, NULL, NULL);
Here s an example that shows how to use the procedure to collect system statistics: SQL> EXECUTE dbms_stats.gather_system_stats('start'); PL/SQL procedure successfully completed. SQL> SQL> EXECUTE dbms_stats.gather_system_stats('stop'); PL/SQL procedure successfully completed. SQL> SQL> SELECT * FROM sys.aux_stats$; SNAME PNAME PVAL1 PVAL2 ------------------------------------------------------------SYSSTATS_INFO STATUS COMPLETED SYSSTATS_INFO DSTART 04-25-2005 10:44 SYSSTATS_INFO DSTOP 04-26-2005 10:17 SYSSTATS_INFO FLAGS 1 SYSSTATS_MAIN CPUSPEEDNW 67.014 SYSSTATS_MAIN IOSEEKTIM 10.266 SYSSTATS_MAIN IOTFRSPEED 10052.575 SYSSTATS_MAIN SREADTIM 5.969