# IBM i (AS/400) Disk Capacity Runway Calculator

> Source: https://netray.co/tools/ibm-i-disk-capacity-runway-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Enter total and used disk, your yearly growth and a threshold to see how many months of headroom you have left.

## Category

erp-operations

## Erp

Oracle JD Edwards World

## Audience

- IBM i administrator
- IT manager
- Capacity planner

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Total usable disk

**Key:** total_gb

**Type:** number

**Default:** 2000

**Min:** 1

**Step:** 50

**Unit:** GB

**Help:** System ASP capacity as shown in WRKSYSSTS or WRKDSKSTS.

#### Currently used

**Key:** used_gb

**Type:** number

**Default:** 1100

**Min:** 0

**Step:** 10

**Unit:** GB

**Help:** Used portion of the system ASP.

#### Annual growth rate

**Key:** growth

**Type:** slider

**Default:** 15

**Min:** 1

**Max:** 60

**Step:** 1

**Unit:** % per year

**Help:** Compare used space a year ago with now.

#### Alert threshold

**Key:** threshold

**Type:** select

**Default:** 80

**Options:**

##### 70% full

**Value:** 70

##### 80% full

**Value:** 80

##### 90% full

**Value:** 90

**Help:** Many shops treat 80 to 90 percent as the line for planning an expansion.

**Outputs:**

#### Threshold in GB

**Key:** threshold_gb

**Expr:** total_gb * threshold / 100

**Format:** number

#### Current usage

**Key:** current_pct

**Expr:** used_gb / total_gb * 100

**Format:** percent

#### Headroom to threshold

**Key:** headroom

**Expr:** max(0, threshold_gb - used_gb)

**Format:** number

**Description:** GB you can still add before reaching the threshold.

#### Projected usage in 12 months

**Key:** used_next_year

**Expr:** used_gb * (1 + growth / 100)

**Format:** number

#### Months until threshold

**Key:** months

**Expr:** if(gte(used_gb, threshold_gb), 0, ln(threshold_gb / used_gb) / ln(1 + growth / 100) * 12)

**Format:** months

**Primary:** true

**Description:** Assumes compound growth at the rate you entered.

**Chart:**

#### Months of runway by annual growth rate

**Type:** line

**X:** growth

**From:** 1

**To:** 60

**Steps:** 30

**Series:**

- months

**Disclaimer:** A planning estimate using steady compound growth. Real growth is lumpy, so add margin for projects, journaling changes and backups held on disk.

## Content

**Intro:** Disk full conditions on IBM i are painful because the system slows and can stop at high ASP usage. This calculator gives you a quick runway in months based on current usage and growth.

**Sections:**

#### How to use it

**Body:** Enter total and used disk for the system ASP, the growth rate you have observed and your alert threshold. Find used disk with WRKSYSSTS, which shows the percent of system ASP used, or with WRKDSKSTS for unit level detail. To estimate growth, compare usage from the same month last year. The primary result is the number of months until you hit the threshold.

#### The formula

**Body:** With compound growth, usage after t years is used times (1 + g) raised to t. Solving for the time to reach the threshold T gives t = ln(T / used) / ln(1 + g). The tool multiplies by 12 to give months. If you are already past the threshold the result is zero. The chart sweeps the growth rate so you can see how sensitive the runway is to the assumption.

**Bullets:**

- t = ln(T / used) / ln(1 + g)
- T = total disk times threshold
- g = annual growth as a decimal
- Result shown in months

#### Reading the result

**Body:** Under 12 months means start the purchase or cleanup now, because hardware lead times and approvals take time. Between 12 and 24 months is a planning zone. Over 36 months is comfortable unless a project is about to add data. Before buying disk, check for cheap wins such as old journal receivers, spool files, save files and unused libraries, which the Db2 for i services query tool can help find.

#### Common mistakes

**Body:** Using total installed disk when part of it belongs to an independent ASP or is reserved leads to false comfort. Taking growth from a single busy month overstates it. Forgetting that journaling, new reporting databases or a larger backup retention on disk can change growth sharply is another mistake. Recalculate every quarter and after major projects.

**Cta:** If you want automated capacity alerts that explain what is growing, Netray can build a read-only monitor over your IBM i catalog data on your own servers.

**Faq:**

#### What disk usage level is too high on IBM i?

**Answer:** IBM i performance and stability can suffer when the system ASP gets very full, and the system has its own storage threshold limit. Many shops plan expansion at 80 to 90 percent. Check IBM guidance for your release and set your threshold lower than the system limit.

#### How do I find what is using the disk?

**Answer:** Query QSYS2.OBJECT_STATISTICS by library and sort by size, check journal receivers, and look at spool files and save files. The IBM i Navigator and Access Client Solutions tools can also show storage by library and object type.

#### Is linear or compound growth better?

**Answer:** Compound is a cautious choice for databases that grow in proportion to business activity. If your growth is a steady number of GB per month, a linear estimate can be simpler: headroom divided by monthly GB added.

#### Does this include backups on disk?

**Answer:** Only if they are in the used figure you enter. Save files and image catalogs on the system ASP count towards usage, so include them or remove them first for a clean base number.

## Search terms

as400 disk space planning, ibm i disk capacity calculator, ibm i storage growth forecast, as400 asp usage threshold, ibm i disk 90 percent full, disk runway calculator, ibm i capacity planning, system asp utilization

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