The RWP*Load Simulator - or rwloadsim - is a programming and simulation tool that can be used for several purposes involving execution of SQL statements using an Oracle database. One of the purposes is reflected in its name and is to simulate database load. However, it really does much more than that, and it is best thought of as a tool that fills in the space between SQL*Plus, OCI (Oracle Call Interface) and scripting done with e.g. the Linux command shell. As it is a command line tool, it is well suited for various types of batch or scripting environments, including but surely not limited to testing, triage, and load simulation.
As a scripting tool, you can think of it as if you had SQL*Plus with a programming language, PL/SQL on the client side or bash with ability to execute SQL. It really is somewhere between those three and can be suited for many different scripting purposes.
As a load simulator, it can be used to execute specified SQL statements in a certain order and fashion specifying different types of random input, with variable run duration and/or execution counts or frequency. At the same time, statistics about execution of the individual SQL statements and/or procedures (combination of SQL statements) are collected and saved in a database schema for later analysis, printing, etc. All this can be done with different connection methods such as dedicated connections or a session pool.
As just one example, rwloadsim can simulate a simple order entry workload, where each order gets an order number from a sequence, has a random number of order lines, and e.g. has a status code that gets one of a set of random values with a certain distribution such as 80% open, 15% on hold and 5% closed.
RWP*Load Simulator includes a programming language, and it therefore has elements from general application programming environments. The programming language has some resemblance with PL/SQL (you can declare and execute SQL statements and do many typical operations on cursors), with awk (data types such as strings or numbers can be freely mixed), and several typical scripting and programming languages (procedures, functions, if/then/else logic, for loops, expressions). It also also includes features for printing, reading or writing to files in a fashion that is very suitable for many kinds of scripting. Similarly, it can be used with typical UNIX pipelines for reading as well as writing. The language also includes regular expression processing with some resemblance to grep and sed. There are also several ways to do modular design, including conditional compilation and include files similar to C.
The way SQL is being processed is similar to how OCI does it with bind and/or define variables, so you can also think of rwloadsim as a way to execute OCI without having to write a C program. In most cases, this is done implicitly by matching bind variable names or select list elements in queries to declared variables, but if required, you have full control of how bind and/or define is done.
As a command line tool (the executable is rwloadsim), RWP*Load Simulator reads one or more RWL files as input, parses and executes these. It is generally multi-threaded, which particularly is useful for simulating load, where threads can represent workers, with execution statistics potentially being saved to a database schema.
The following very simple example shows some of the basic features of rwloadsim. Consider a file with this contents:
# Tell how to connect to the database
database scott
username "username" password "{password}"
connect "//hostname/service"
default;
# Declare some variables, and possibly initialize them
integer empno, deptno:=10, numemps:=0;
string ename;
# Tell that a variable can get a value from the command line
$useroption:deptno
# Execute a query as a cursor loop
for
select empno, ename from emp where deptno=:deptno;
loop
printf "%12s %4d\n", ename, empno; # print something to stdout
numemps += 1; # count the number of rows
end loop;
if numemps=0 then # If there were no rows, print a message
printline "No employees in department", deptno;
end if;
If the file were named scott.rwl, you could execute rwloadsim with this file as argument, and you might get:
$ rwloadsim scott.rwl
RWP*Load Simulator Release 3.0.0.25 Development on Tue, 17 May 2022 11:39:58 UTC
RWL-206: warning: OCI compile environment (21.5) is different from runtime (21.3)
Connected scott to:
Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
CLARK 7782
KING 7839
MILLER 7934
If you wanted to execute the same, although specifying a different value of deptno, you might get:
$ rwloadsim --deptno=42 scott.rwl
RWP*Load Simulator Release 3.0.0.25 Development on Tue, 17 May 2022 11:39:58 UTC
RWL-206: warning: OCI compile environment (21.5) is different from runtime (21.3)
Connected scott to:
Oracle Database 21c Enterprise Edition Release 21.0.0.0.0 - Production
No employees in department 42
We will shortly elaborate more on this example.
The RWP*Load Simulator is not a complete application programming tool, and it should not be used as such. If you attempt using it beyond its design purpose, you will realize that it does have limitations compared to traditional application programming environments. Some examples are a complete lack of GUI, relatively simple input, several programming capabilities found in many other programming language are missing, only few simple data types are supported. That said, it does support a modular programming approach that is suited for the purpose of simulating load, and it does allow relatively advanced scripting in particular when combined with shell scripts.
These are design criteria and you should not expect rwloadsim to evolve into a complete application programming tool. However, within its bounds, it can be a very efficient scripting tool, including for the type of scripts typically used by database administrators. As said, if you ever wanted to have bash, sqlplus and pl/sql integrated into one utility, rwloadsim may be exactly what you are looking for. It should also be mentioned that the developers always are open for new ideas.