Category: ZIM-X Database Management

Because Zim 9 always operates in the client/server mode, memory operations performed by the client are not affected by what is being done in the server and vice-versa.

When running Zim on Windows in the client side, the local machine is dedicated to the client session; therefore, all resources available can be used solely for Zim. Consequently, memory is not a concern and the administrator can set configuration options to the maximum in order to improve performance.

The configuration options file for the client is the zimconfig.zim (the database configuration file) and the most relevant options are Maximum Forms, Maximum Form Fields, Runtime Buffers and Sort Buffers. These options can be set to their maximum values all the time. Other parameters like Directories, Document Line Length, Maximum Parameters and Parameter Size can be set to a size according to the needs of the application and can be left to their initial and default state, only changed if Zim states an error.

On the other hand, Zim sessions running on Unix will compete for memory and resources with all other Zim sessions and, most important of all, with Zim Server and its shared memory. Therefore, the administrator must balance the needs of Zim Server and the needs of Zim sessions. Thus, for Unix, the options Runtime Buffers and Sort Buffers must be privileged. The other options (as mentioned for Windows, above) can be configured to some values that still allow Zim sessions to run comfortably without expending too much memory. In general, these values are the default ones that can be changed depending the needs of the application.

Optimizing Memory Usage for Faster Response Times

If all the files an application needs at any given time could be stored in memory, response times would be significantly faster. Accessing main memory is much quicker than using disk input/output (I/O) because disk access times are much longer. However, in practice, it is impossible to keep everything in memory, especially if a database contains millions of records.

Efficient Data Transfer Between Memory and Disk

During an application session, much of the data must be continually transferred between memory and disk. This includes data stored in the database, database definitions, screen definitions, and application programs.

Controlling Data Locks

Maximizing disk access is crucial, but so is controlling locks over the data being processed by each user once it is available in memory. This topic is discussed in detail in the Locks and Deadlocks Conditions section.

Zim Server Efficiency

Zim Server’s efficiency relies heavily on the available memory allocated for its use. When Zim Server starts, it reads its configuration file, calculates the required memory, and allocates the corresponding shared memory for client connections.

Shared Memory Allocation

Shared memory is allocated using a mapping mechanism that associates an address space with physical memory. If the available real memory is sufficient to accommodate the allocated shared memory, Zim Server operations will be highly efficient. If not, the operating system will need to swap out and swap in portions of shared memory that do not fit in the real memory.

Impact of Swap Operations

Although swap operations are faster than regular file operations, they are still slower than real memory operations. Therefore, administrators must consider this factor when configuring Zim Server.

Configuration Options for Efficiency

All Zim Server configuration options address efficiency issues. Key options include Checkpoint Buffers, Checkpoint Transactions, Clustered Commits, Maximum Blocks per User, and Maximum Data Blocks.

When considering the performance of an application, individual users have different criteria in mind. To some, performance is the speed at which an application responds to the requests of an application user. To others, it is the ability of the application to run properly within the limits set by the hardware or operating system. Performance can also be seen as the overall ability of a multi-user application to process a great deal of work for a large number of users quickly and efficiently.

Performance tuning attempts to maximize the success of an application in achieving the criteria described above. Performance tuning can be done by altering the design of the database, using different coding techniques, modifying the design of multi-user transactions, changing the configuration of the operating system, and altering the software’s own configuration. The focus of this section is solely on altering the software’s configuration to fine-tune performance.

To increase the performance of any application, four areas should be considered:

The utility ZimAdmin can help with the dimensioning of the configuration options by dynamically  monitoring the status of ZimServer, just like this example: