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Differences will be caused by different Oracle versions, different operating systems, or different hardware platforms. The idea will be the same, but the exact numbers will undoubtedly be marginally different.

Now, the preceding result clearly shows that based on CPU time, it took significantly longer and significantly more resources to insert 10,000 rows without bind variables than it did with them. In fact, it

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Table 10-2 shows the primary namespaces in .NET Framework DLLs from Table 10-1. In some cases, parts of these libraries are covered elsewhere in this book. We ve noted these cases in the table. For example, 4 introduced portions of the .NET I/O library from the System.IO namespace.

took almost 20 times as much CPU time to insert the rows without bind variables. For every insert without bind variables, we spent the vast preponderance of the time to execute the statement simply parsing the statement! But it gets worse. When we look at other information, we can see a significant difference in the resources utilized by each approach: Name STAT...parse count (hard) STAT...parse count (total) STAT...consistent gets from ca STAT...consistent gets STAT...consistent gets from ca LATCH.simulator hash latch STAT...db block gets from cach STAT...db block gets STAT...db block gets from cach LATCH.enqueues LATCH.enqueue hash chains STAT...session logical reads STAT...recursive calls LATCH.kks stats STAT...session uga memory STAT...session pga memory LATCH.cache buffers chains LATCH.shared pool simulator LATCH.row cache objects LATCH.shared pool LATCH.JS slv state obj latch Run1 5 34 78 135 135 83 10,440 10,440 79 40 74 10,575 10,326 23 0 0 51,532 42 294 20,302 1 Run2 10,010 10,055 10,120 10,290 10,290 10,990 30,364 30,364 20,041 20,372 20,414 40,654 40,960 65,141 65,512 65,536 120,773 104,558 184,697 446,397 435,890 Diff 10,005 10,021 10,042 10,155 10,155 10,907 19,924 19,924 19,962 20,332 20,340 30,079 30,634 65,118 65,512 65,536 69,241 104,516 184,403 426,095 435,889

Run1 latches total versus runs -- difference and pct Run1 Run2 Diff Pct 73,082 1,411,695 1,338,613 518% PL/SQL procedure successfully completed The runstats utility produces a report that shows differences in latch utilization as well as differences in statistics Here I asked runstats to print out anything with a difference greater than 10,000 You can see that we hard parsed 4 times in the first approach using bind variables, and that we hard parsed over 10,000 times without bind variables (once for each of the inserts) But that difference in hard parsing is just the tip of the iceberg You can see here that we used almost 20 times as many latches in the non-bind variable approach as we did with bind variables That difference might beg the question What is a latch Let s answer that question.

Types and methods that define commonly used value and reference data types, events and event handlers, interfaces, attributes, and processing exceptions, supporting data-type conversions, mathematics, application environment management, and runtime supervision of managed and unmanaged applications. See 3 for many of the basic types in this namespace. Types that can be used to represent the elements and structure of a source code document. Not covered in this book.

A latch is a type of lock that is used to serialize access to shared data structures used by Oracle The shared pool is an example; it s a big shared data structure found in the System Global Area (SGA), and this is where Oracle stores parsed, compiled SQL When you modify this shared structure, you must take care to allow only one process in at a time (It is very bad if two processes or threads attempt to update the same in-memory data structure simultaneously corruption would abound) So, Oracle employs a latching mechanism, a lightweight locking method to serialize access Don t be fooled by the word lightweight Latches are serialization devices, allowing access one process at a time The latches used by the hard-parsing implementation are some of the most used latches out there These include the latches for the shared pool and for the library cache.

Table 10-2. Namespaces in the DLLs from Table 10-1, with MSDN Descriptions (Continued)

Those are big time latches that people compete for frequently What all this means is that as we increase the number of users attempting to hard parse statements simultaneously, our performance gets progressively worse.

Table created. ops$tkyte%ORA11GR2> ops$tkyte%ORA11GR2> select segment_name, segment_type 2 from user_segments; SEGMENT_NAME -----------------------------T SYS_IL0000093076C00002$$ SYS_IL0000093076C00003$$ SYS_C0019048 SYS_LOB0000093076C00002$$ SYS_LOB0000093076C00003$$ 6 rows selected. SEGMENT_TYPE -----------------TABLE LOBINDEX LOBINDEX INDEX LOBSEGMENT LOBSEGMENT