Here is a guide on how to do so using vmstat, which provides real-time statistics about system performance and resource utilization.

1. Understanding the Output of vmstat:
Active and Inactive Memory: If you use the `-a` option with `vmstat`, the buff and cache memory columns are replaced by “inact” and “active” columns, which show the amount of inactive and active memory respectively. The unit for these values is blocks.
Forks: This switch displays the number of forks that have happened since the computer was booted up. Each time a task or process spawns or clones a new task, this figure will increase.
Displaying Slabinfo: To see statistics related to slabs (pre-allocated segments of RAM for kernel data objects), use the `-m` option with `vmstat`. This displays five columns: name of cache, number of currently active objects in that cache, total available objects in that cache, size of each object in the cache, and total number of memory pages associated with this cache.
Displaying Event Counters and Memory Statistics: Use the `-s` option to display a page of event counters and memory statistics. This provides more detailed information than the default output, including separate listings for nice and non-nice user CPU time.
Displaying Disk Statistics: To obtain similar disk statistics as vmstat’s default output, use the `-d` option with `vmstat`. Three columns are displayed: Reads (total count of reads), Writes (total count of writes), and IO (current number of in-progress reads or writes, time spent in seconds for any in-progress reads or writes).
Displaying Summary Disk Statistics: Use the `-D` option to see a quick display of summary statistics for disk activity. This can be useful when trying to diagnose issues with disk performance.
Displaying Partition Statistics: To view statistics related to a specific partition, use the `-p` option and provide the partition identifier as a command line parameter.

2. Tips for Optimizing Memory Usage in RHEL 7.6:
Use vmstat to monitor system performance and resource utilization. This can help identify areas where memory usage is high or resources are being underutilized, allowing you to make adjustments as needed.
Monitor the “inact” column when using `vmstat` with the `-a` option. If this value is consistently higher than the “active” column, it may indicate that there is room for improvement in memory usage.
Use slabs (pre-allocated segments of RAM) to improve kernel data object management and reduce fragmentation. Monitoring slab statistics using vmstat can help identify areas where slabs are being underutilized or overused.
Optimize disk performance by monitoring IO statistics using `vmstat` with the `-d` option. This can help identify areas where disk usage is high, allowing you to make adjustments as needed (such as adding more storage space).

To optimize memory usage in RHEL 7.6, there are several techniques that can be employed using vmstat, a tool for real-time statistics about system performance and resource utilization. Here’s how:

1. Understanding the Output of vmstat:
Active and Inactive Memory: If you use `vmstat` with the `-a` option, the buff and cache memory columns are replaced by “inact” and “active” columns that show the amount of inactive and active memory respectively (measured in blocks). This can help identify areas where memory usage is high or resources are being underutilized.
Forks: The `-f` switch displays the number of forks that have happened since the computer was booted up, which can be useful when trying to diagnose issues with task and process management.
Displaying Slabinfo: Use the `-m` option with `vmstat` to display statistics related to slabs (pre-allocated segments of RAM for kernel data objects). This displays five columns: name of cache, number of currently active objects in that cache, total available objects in that cache, size of each object in the cache, and total number of memory pages associated with this cache.

To optimize memory usage in RHEL 7.6 using vmstat, here are some tips:
Monitor system performance and resource utilization by running `vmstat` regularly to identify areas where memory usage is high or resources are being underutilized.
Use the “inact” column when monitoring memory usage with `vmstat`. If this value is consistently higher than the “active” column, it may indicate that there’s room for improvement in memory usage.
Optimize kernel data object management by using slabs (pre-allocated segments of RAM) to reduce fragmentation and improve performance. Monitoring slab statistics with `vmstat` can help identify areas where slabs are being underutilized or overused.
Use the “forks” switch when running `vmstat` to monitor task and process management, which can be useful for diagnosing issues related to launching new tasks or processes.
Monitor disk performance by using `vmstat` with the `-d` option to view IO statistics. This can help identify areas where disk usage is high, allowing you to make adjustments as needed (such as adding more storage space).