ASP.NET Web PDF Document Viewer/Editor Control Library

For very large databases or for databases performing intensive operations, a single database writer process may be inadequate to perform all the writing to the database files. Oracle provides for the use of multiple database writer processes to share heavy data modification workloads. You can have a maximum of 20 database writer processes (DBW0 through DBW9, and DBWa through DBWj). Oracle recommends using multiple database writer processes, provided you have multiple processors. You can specify the additional database writer processes by using the DB_WRITER_PROCESSES initialization parameter in the SPFILE Oracle configuration file. If you don t specify this parameter, Oracle allocates the number of database writer processes based on the number of CPUs and processor groups on your server. For example, on my 32-processor HP-UX server, the default is four database writers (one database writer per eight processors), and in another 16-processor server, the default is two database writers. Oracle further recommends that you first ensure that your system is using asynchronous I/O before deploying additional database writer processes beyond the default number you may not need multiple database writer processes if so. (Even when a system is capable of asynchronous I/O, that feature may not be enabled.) If your database writer can t keep up with the amount of work even after asynchronous I/O is enabled, you should consider increasing the number of database writers.

barcode creator excel 2007, activebarcode not in excel, barcode add in for excel 2010, free barcode generator excel 2013, free 2d barcode generator for excel, how to print 2d barcode in excel, microsoft excel barcode generator software, microsoft excel 2010 barcode add in, free qr barcode font for excel, free excel 2d barcode font,

The job of the log writer (LGWR) process is to transfer the contents of the redo log buffer to disk. Whenever you make a change to a database table (whether an insertion, update, or deletion), Oracle writes the committed and uncommitted changes to a redo log buffer (memory buffer). The log writer process then transfers these changes from the redo log buffer to the redo log files on disk.

The log writer writes a commit record to the redo log buffer and writes it to the redo log on disk immediately, whenever a user commits a transaction. The log writer writes all redo log buffer entries to the redo logs under the following circumstances: Every 3 seconds. When the redo log buffer is one-third full. When the database writer signals that redo records need to be written to disk. Under Oracle s write-ahead protocol, all redo records associated with changes in the block buffers must be written to disk (that is, to the redo log files on disk) before the data files on disk can be modified. While writing dirty buffers from the buffer cache to the storage disks, if the database writer discovers that certain redo information has not been written to the redo log files, it signals the log writer to first write that information, so it can write its own data to disk. The redo log files, as you learned earlier, are vital during the recovery of an Oracle database from a lost or damaged disk.

ostype=`cat /proc/sys/kernel/ostype` osrelease=`cat /proc/sys/kernel/osrelease` rev=`cat /proc/sys/kernel/version | awk '{print $1}'` da_date=`cat /proc/sys/kernel/version | cut -d\ -f2-` upsec=`awk '{print $1}' /proc/uptime` uptime=`echo "scale=2;$upsec/86400" | bc`

The checkpoint (CKPT) process is charged with telling the database writer process when to write the dirty data in the memory buffers to disk. After telling the database writer process to write the changed data, the checkpoint process updates the data file headers and the control file to indicate when the checkpoint was performed. The purpose of the checkpoint process is to synchronize the buffer cache information with the information on the database disks. Each checkpoint record consists of a list of all active transactions and the address of the most recent log record for those transactions. A checkpointing process involves the following steps: 1. Flushing the contents of the redo log buffers to the redo log files 2. Writing a checkpoint record to the redo log file 3. Flushing the contents of the database buffer cache to disk 4. Updating the data file headers and the control files after the checkpoint completes There is a close connection between how often Oracle checkpoints and the recovery time after a database crash. Because database writer processes write all modified blocks to disk at checkpoints, the more frequent the checkpoints, the less data will need to be recovered when the instance crashes. However, checkpointing involves an overhead cost. Oracle lets you configure the database for automatic checkpoint tuning, whereby the database server tries to write out the dirty buffers in the most efficient way possible, with the least amount of adverse impact on throughput and performance. If you use automatic checkpoint tuning, you don t have to set any checkpoint-related parameters.

Figure 7-4. Choosing performance counters from the .NET CLR Memory performance object In case you experience other problems with assembly startup, you will likely find useful information in 12.

When user processes fail, the process monitor (PMON) process cleans up after them, ensuring that the database frees up the resources that the dead processes were using. For example, when a user process dies while holding certain table locks, the PMON process releases those locks so other users can use the tables without any interference from the dead process. In addition, the PMON process restarts failed server processes and dispatcher processes. The PMON process sleeps most of the time, waking up at regular intervals to see if it is needed. Other processes will also wake up the PMON process if necessary.