# xSQL Storage Usage

> Sometimes it is useful to see the amount of database memory or persistent storage space that is available in the database. xSQL provides the `mem` and `memddl` commands for this purpose.

> ### For an overview see page xSQL Server Instrumentation

> ## Command mem

> The `mem [-b|-k|-m|-g|-t|-p]` command displays the amount of total and free storage in the database. The available storage is displayed in bytes (-b), Kilobytes (-k, default), Megabytes (-m), Gigabytes (-g), Terabytes (-t) or memory pages (-p). For example, the following displays memory usage for an in-memory database:

>         XSQL>mem
>         Total         Used               Free
>         Mem :    102212            6      	     102205

>         XSQL>mem -b
>         Total         Used               Free
>         Mem : 104665344         6656       	  104658688

> The following for a persistent database:

>         XSQL>mem
>         Total            Used            Free
>         Mem :    102154              12          102141
>         Disk:       128             121
>         Log :       833

> ## Command memddl

> Similarly the `memddl` command displays the memory reserved and used for database classes and indexes, and for the database dictionary. For example:

>         XSQL>memddl
>         Reserved             Used        Available
>         Classes    :              100                1               99
>         Indexes    :             1000                1              999
>         Dict. size :             32Kb              1Kb             30Kb